heh, i just came from my economics class. basically, you got to buy stuff as well as accept the rent. you buy more stuff, you raise demand, which will raise the economy level, which raises prices, which lowers demands, lowers prices, and repeat. or something like that.
taking all the town's money is a great way to put it in the pits. invest a lot of money into the town, like 50% or more of what you earn from it, and you should be fine.