wow, what a great idea!
Almost everything you're asking about is going to depend on where you decide to locate your hostel. Zoning laws / et al are different all over the place, sometimes they can change neighborhood by neighborhood within a particular city (no shit.) So the best thing to do would be scope out a few places that you would like to do this and then look into the info for each place, including getting a pre-approval for a loan. Good luck and keep us updated how it's going! We'd love to hear about it!