The next campaign I run will focus on the heroic adventures to be had while running your own small business. Basically, the party will inherit an old, run-down inn from their estranged relative. He is somehow related (through the use of his long elven life and polymorph and enchantment magic) to all the party members (who will meet for the first time when they all show up to claim their inheritance thinking they are the sole beneficiary).
There will, of course, be a wide variety of monster slaying and traditional fare, but my players really get into the economics of a world. The Pathfinder rules fail in providing this sort of simulation. The main problem I'm running into is that magic items (what the PCs will be hoping to buy with their profits) are so much more expensive than a mug of ale. The first thing I intend to do is drop a zero off the end of all masterwork and magic item prices and give my players far less gold so that it's a little more meaningful. A 245gp +1 longsword is actually in within their grasp if they save up their tips. As-is, magic items are just too expensive, considering they practically litter the landscape.
I also plan to have random events, such as:
-Dwarves show up: who stereotypically drink far more ale than normal customers.
-Taxation: the greedy local lord sends his tax collector to their door (maybe the PCs will allow him to take their gold only to don masks and rob him in the forest).
Does anyone have any other ideas to make this a fun and rewarding mini game?
You might be able to adapt the rules for kingdom building into business building. For example, change the government positions to business positions, change the buildings into additions, and have the events be stuff that happens in a tavern. The GP value of BP would need to be adjusted as well. Overall, this might be the best hands on approach. It doesn't involve a great deal of attention (thus it doesn't detract from the game,) but it still has some micromanagement.
You can find the kingdom building rules in Kingmaker or The Book of the River Nations. The second book has expanded the rules a bit and it doesn't have spoilers.