I figure if they can't afford to buy it, they can't afford to borrow it and I can't afford to lend it to them.
I have ONE buddy that I loan my tractor to. He has his own auto repair shop and an OLD 680 (?) Case 2wd loader/hoe that he rebuilt. The Case is sitting in my driveway tonight after I borrowed it to install MY geothermal pipe out into our lake. My little hoe only reaches 7ft. His reaches 15ft (or so).
Normally I will help anyone do any job that they need, but I DRIVE my machine...If they are paying me to do the job, then I repair any hoses I blow. If I am doing it as a favour then its nice if they chip in.