I have a hard fast standing rule with anyone that rides any of my toys and it goes both ways. You break it you buy it, if they don't agree to that or I think they can't afford that then they don't ride. I have bought a front shock for a blaster (may have been normal wear and tear but it broke when I was riding it) Also chipped in on a front axle and radiator for and old jeep, that was fun we took that baby airborne.
Knock on wood I have not had any of my toys broken yet, but only a few have been ridden/used by others they just haven't asked.
That is my 2 cents.