Illegal for an individual to rent to you without the proper insurance. Unlikely someone will lend to you since any claims would go on their record. But plenty of people break both those rules, I think.
Edit: Just saw the post about GTAExotics. Didn't know there was a fairly affordable place to get them now. Last I saw it was way expensive and was only supersports.
I just read over my shiny new policy and I'm covered if I lend the bike to a licensed person and they have a crash. If I take money for it my policy is void.