That kind of depends on how much traffic you expect, what's available in your area, whether they'll like you being a site host, and how much you want to spend. Costs more to be a commercial site than it does to be a home user site, also, generally, costs more for a fixed-IP address than it does for a dynamic address.
DSL on copper runs at about 150K to 180K speeds, shouldn't cost more than about $20; the speed goes up if you have fiber optic but so does the price (there are different levels of DSL service most places). Satellite runs a little faster than DSL copper and costs about $50 a month for "home" use, more for commercial use (if you buy the equipment). Cable TV providers are faster than DSL but they charge a lot after the "introductory" period for home use and who knows how much for commercial use and many of 'em aren't all that reliable; i.e., ask around. Then, you've got T1 from the phone company and that's probably more than your house payment.
You could, possibly, get away with fiber-optic DSL service if you're not going to be hosting high demand users (like video feeds and the like). That ought to be less than $100 (check your local suppliers). Maybe cable if the company is reliable (if your TV service is down frequently, so will your internet service be). Hughes Net and other satellite provides offer different levels of service and they're, generally, 24-7 but can go away when there's a real heavy storm (but generally for not that long a time); they can cost from, you know, $50 on up.
If you want to be an ISP, that's T1 and that's a lot of bucks (you pay by the foot to get the wire strung to your facility then you pay a hefty fee per month).
Hope this helps some.