Last year an internet friend asked me where he could rent a bike in Germany with which he could tour for a few weeks, thereby avoiding the hassle of bringing his own bike on the plane from America. I told him I didn't know where he could rent one, but that he could use my wife's touring bike for his trip. I told him he didn't have to pay me a cent for using it, but that he would need to leave a deposit with me while he was touring.
It went off without a hitch, and it made me think....... Why don't I offer that "service" to anyone?
So, that's what I'm gonna do. If you come in and out of Frankfurt, I have 2 touring bikes available to be lent. No charge, just the deposit which you get back when you return the bikes.
EDIT: Now, in addition to the three touring bikes, a tandem is available for "lental". Uh, I mean, loan.