ok...
to start a wired dialup ISP you'll need...
aseries of phone lines attached to modems, that are attached to a computer or router with a high speed connection...
to start a wireless connection ISP you can do away with the wires and modems in favour of wireless connections...
asuming you only customers are in your house you'll need a wreless access point, this will set you back about £30...
assumnig you want to server slow speed internet on a very slow and low region scale a few GPRS transiever masts would be good...
setting you back a few hundred per mast, and then yearly broadcasting regulations...
assuming you want to serve high speed internet on a wide scale, then you're going to need a large payroll and a satalite...
you'll also probably have to pay for / lease the equipment going into peoples houses as well since satalite base stations don't really come cheap...
There is a sligh possibility that you could probably rent some bandwidth frmo a larger company on their network, but even that is expensive...