If I built it...would you come?
Yes, and bring a friend.
How often?
At least monthly, perhaps more if you offered other things such as clubs, leagues, contests, etc.
How much would you pay per hour or half hour?
Depends on the services, range size, ammo cost. Also would you offer a yearly membership? Special discounts to NRA? etc.
Would you want leagues?
Yes. A ladies league would be awesome.
Instruction?
I think that would be a valid thing to offer and increase your business. Not only gun safety and hunter's safety, but a course geared towards first time shooters (you'd be surprised by the amount of females I know that would love to learn to shoot), as well as "special" instruction such as trick shoot, competition, etc. I bet if you were to contact the NRA, they would also be willing to bring in classes to your location.
Gun rentals?
Ugh, that one's tough. I think the laws, and insurance for that would be astronomical. I would check with the local laws, as well as state laws. I'd be scare of what your insurance person would say. Not to mention, you have one non-responsible bozo in there goofing off with your gun and there goes your business.
Ammo available?
Every indoor range I have ever been to makes you buy your own ammo there and use it there. I believe this is logical because you don't want somebody coming and using high explosive, armor piercing etc rounds, which would have the potential of causing harm or destroying your place of business.
any other input?
Depending on how large your facility is, you could also set up a shop that includes supplies (ammo, clips, holsters, ear plugs, etc.), magazines, etc. Also if the location is large enough it would have the potential to grow for use of indoor paintball, or miles type gear ranges where "teams" could secure a tactical objective. Those things are fun.