Good advice from Torres.
We did just that a few years ago. and just like a car rental company, our agreement stated that the hirer is/was liable for any excess (usually 1% of hull value) regardless of fault.
Just like a car rental company, we used to take a signed credit card swipe or imprint prior to flight.
Of course renters will complain but just point out that hotels, airlines, car rental companies all require credit cards up front.
If you dent a rental car - the excess will be taken out of your credit card account. Even if it wasn't your fault. (tip; report dents in rental car before accepting it - doh!, my hard learnt lesson)
Also comes in handy if the renter skips payment or 'forgets' landing fees and refuelling charges. Abandons an aircraft in the middle of nowhere or does something totally unexpected.
Years ago we tried to charge an insurance excess after the fact - and you guessed it, not a snowflakes chance in hell of getting the money.
I.J. - cover yourself from all angles, even at the risk of offending some renters. It will help you sleep at night when a renter has your aircraft on an extended trip. (BTW; only one lost customer in years due to the credit card policy).