So my players all really want to make a town/city that involves farming, raising livestock, mines, setting up a town guard ect. I have a lot of ideas for the story and great roleplaying elements that would further the story but I need help on how to balance everything.... I want it to be something they work at over time to build up into something great. One big question is say they have goblin slaves working in there mines what is a way to tell the players how much money that mine would make in a 10 day? i would want them to roll for it as you wouldent make the same everytime. Anyway just looking for ideas or maybe something someone is the past has done that was fun 
At this scale you probably don't want to be rolling for every day, as it's going to take years to build a city.
I'd elevate all the downtime activities one or two steps. 'Working in the smithy making a weapon for the day' becomes 'working with the town's smiths to create gear for a month.'
You could also avoid exact profit numbers by saying, "The mine will bring in enough money to fund one of your expansions, what do you want to build in the city?"
I can see this being really fun actually, taking a small settlement through a number of years of growth. Each PC taking a leadership role in varying areas of the city and coming together to deal with problems that arise. Game sessions could cover those particularly serious events that require their attention but might have months of in-game time pass between them.
If you and your players want to focus on the economic specifics then I would check out the Downtime activities section of the PHB to see how much profit a single person can make in a day's labour.
I actually did this kind of thing for my players who want to rebuild Tresendar Manor (LMoP module) and found that they would have to hire 24 men for 83 days and it would cost 5996 gold to build a house of "Longship" complexity/size.
That is exactly what my group is looking for! I was also going to reward them with the manor after clearing out the bandits one of the PC's is a half Orc and his main goal is acquiring his own warband of goblins,orcs,ogres,trolls and giants. We've had a ton of fun with it so far but all he has is some Lonley goblins haha! That's when the idea hit to slowly start a base and aquire better gear and more numbers thru mining and agriculture
One thing I would think about is when they hire people those people could possibly stay or drive others to follow. So like 25 men bring another 20 people with them and on their own they build an inn or a general store. Like the players don't need to build/design every inch of the town some of it would grow organically. I'm really excited to see how you guys make this work.
The Pathfinder adventure paths had rules for this at one point. They worked fairly well, it used turns (not combat turns, I think they were 1 month) and at the end of each turn the PCs made choices such as what buildings they built, who they put in charge/hired for certain city positions and such. They worked really well when I used them.
Adventure Path 32: Rivers Run Red is the one that had the specific crunch you need. Though I encourage you to take a look at the entire adventure path, it's all about the PCs going into a wild area and building a town from the ground up. Which sounds a lot like what you are doing. The ideas you could pull from this are endless.
I think you guys are on the right track and it sounds like a lot of fun. They probably don't really want to manage the day-to-day operations of a town too much - they want to make fun choices that have an impact on it's growth and they want it to be the backdrop for adventure, right? So my advice is to look for interesting and tough 'big picture' decisions for them to make, then try to tie them into adventure plot hooks.
For example:
Production from the goblin mines has dropped significantly the past few weeks and the foreman says that if he doesn't get more guards soon, there might be a rebellion. Meanwhile, farmers near the forest are reporting that something strange has been coming out of the woods at night and is ruining their crops. They need to protect the fields or else there will be a food shortage after harvest, and they have requested that a watchtower be built and town watch be assigned. The town doesn't have the resources for either problem without pulling them from somewhere else. What's more important to the town - food or money? What's going on in the mines that is disturbing the goblins? What's coming out of the woods at night? Are the PCs going to get involved in one of these issues directly while trying to mitigate damages from the other? Or are they going to try something you haven't thought of, like go barter a deal with the next town over for some temporary help?
I looked into it and your right has a lot of what I think we're aiming for, the cool part is we don't have to strictly focus on building the settlement. so far they've made some construction decisions and hired labors to get things started, while the building is happening they pick up the adventure they left off on and periodically get messages by raven or courier with details on how it's all going and sometimes a side quest that needs there attention, Orc raiders attacked, laborers turn up missing, ect to keep it fun they also have been telling people they rescue/help about there settlement and encourage them to make a fresh start there. Lotta fun so far!
Ansbach wrote:
Could also do a point system. Instead of number crunching gold, make the numbers smaller. The mine produces 3 stone per week, the lumberjacks produce 2 wood per week (can push for 3 at risk of angering locals druid cabal)....then houses take 1 stone and 2 wood to make. Those aren't solid numbers, just my idea.
If you don't like that, then you can use a monetary system basically doing the same. House takes 800 gold worth of wood and 200 gold worth of stone. The querry produces 500 gold worth of stone each week and the mill gives out 1000 gold of wood per week.
Ive been doing something similar with my campaign. The PCs are trying to bring stability back to a region of their country by rebuilding a fallen town/keep. In my game they can donate a portion of their funds earned from adventures to repair the keep. As the keep is repaired they gain acces to new functions like a proper temple, arcane library, more accessable trade routes and more fortresses scattered througout the region. Most of the actual repairs and things are handles by NPC's but the PCs are responsible for hiring people to various roles, and negotiating contracts.
Whatever crunch it is you use, I think the important bit is to not get bogged down in details and to use the city as a way of driving adventure rather than distracting from it.
IIRC (long time ago), there was a Castle Builder's Handbook for AD&D. You might be able to find a copy on eBay or at a convention. The (equally old) World-Builder's Guidebook had an abstract system to build up a town - or even nation - from scratch.
As pointed out above, do NOT turn this into something only an accountant would love. Be sure to add a line of descriptive text when the PCs come back home of what's different - a new inn under construction, a dwarf smith set up shop, gypsie caravan stopping by to check out the possibilities, farmer's market stretches along a whole city block and cramps traffic, the newly-acclaimed mayor, ambitious merchant with log of mahogany (not oak) for sale, somebody built a slum block oops.
I was in a campaign of Savage Worlds: Deadlands (Weird Wild West) that had something similar. We inherited a ranch and had great fun in deciding things like if we were going to raise cattle or horses. One adventure was a cattle drive with the herd harrassed by werewolves. It was like Undead Bonanza - good stuff!
If you are looking for resources on this kind of thing one of the last good books by Gary Gygax was call Living Fantasy, from Troll Lord Games. It's a bit rare and hard to find, but worth tracking down - along with Nation Builder.
The biggest thing that pops out to me is the the want of your PC to involve many races of evil humanoids. Though I get it (kind of), I think that it'd be the biggest impact on the town than anything else. What kind of people do you think a place like this would attract? How long would it take for other communities to band together to drive you out? Of course these all have to do with your setting. Maybe this is common practice, but in a place like the Forgotten Realms, you're gonna have some trouble. Especially if it in the Sword Coast North with Obould's kingdom recently causing so much havoc already.
This sounds a lot of fun. A fledgling frontier town is a great setting which could throw up all sorts of adventure ideas. The first thing that popped into my head was HBO's Deadwood which would be a great resource - lots of ideas for complications. The players could have to deal with problems in the mines, raiders from the wilderness, organised crime gangs trying to move in, labour disputes, keeping some sort of order in the town, dealing with interference from the 'authorities' (Neverwinter or the Lords Alliance) wanting to annex it or just introduce taxes and regulations, defending it from attack, all sorts of stuff.
Danny above is right that the prevalence of orcs and humanoids is an interesting twist, particularly of you're using the module's original setting near Neverwinter. Is the intention to turn it into a cosmopolitan place which acts as neutral ground so that normally antagonistic factions can trade and negotiate, or is it going to end up more of a lawless bandit town? Could be interesting either way.
That's why I was excited to get it set up the possibilities and conflicts I could throw at them are endless and a lot of factors could be used, love all the ideas and references so far thanks guys! They should really make an official module like this I think it would do great, I know they've kinda done it in the past with the castle builder. So far they've set up a small mine with 6 goblin laborers that are overseen by a well paid hobgoblin and they have convinced a small band of halflings to set up some farms to start there agriculture needs. They are currently dealing with a nomadic tribe of centaurs for possible trade opportunities when they pass near by
Building a city sounds really fun!
There seems to be a lot of good advice in this thread, and I would also suggest that you consider holding off some of the details until the DMG arrives. The DMG should have rules regarding domain management etc, so I would be a bit disappointed if the DMG does not contain a lot of the relevant rules for this situation. But if you do make or find your own rules before the DMG and is happy whith them that is great!
The answer of what you should do depends on what level of detail you want.
Do they want to just have a city as a home base, or do they want to actually manage a city's development? In terms of video game genres, are they looking for an RPG where they own a city, or are they looking for a strategy/sim game?
If the first, then the advice given in this thread is good. If they don't want to manage its actual development, then all you need to do is consider it in terms of adventure hooks.
If the second, however, then they need more detail than that. I have used three systems in the past for this sort of thing; Pathfinder's Kingmaker (which can be found standalone in Book of the RIver Kingdoms), AD&D's Birthright, and ACKS. For managing a single city, I would choose one of the first two (ACKS uses a larger scale and wouldn't scale down in an interesting way). Kingmaker and Birthright both have the variance in different building types that can be used to figure out the general effects of choices on a small scale.
It is also possible that the DMG will have something for this sort of thing.