i'm quite sure you do need a license.

To run an ISP you probably have to keep yourself protected from lawsuits and such, so be sure you reserve rights to cancel installations and stuff like that.

you'd need to purchase a line, from one of the companies that supplies them to ISP's. I know of one company for the area in which I live...

you will need some $$$ to start up, as with any business.

i think that basically you become a reseller of bandwidth, just as there are resellers of products that you buy from the store.

you should probably do some googling.