I know this sounds condescending, but just asking these questions means you are under-qualified to open such a high-risk business. You want a carefully-crafted waiver AND the protection of a corporation AND proper business insurance. Each of these is going to require a fair degree of time/expense to do properly. If you don't have the startup capital to make it work, look into a different business. Renting any vehicle to strangers, even a cruiser bike, is serious business with serious legal consequences, especially in the litigious USA.

If you haven't done so yet, I'd also try and find others who are doing the same business and ask for advice, even if you have to go quite a ways away to find someone who will talk to you.

- Mark