I spend a lot on decent tools and try to keep them clean. Over the years I have found that (my) customers work on the assumption that a decorator with paint-free clothes and tools is less likely to make a mess in their homes.
If I lend tools to someone, I expect them to get the back in the same condition that I lent them. That said, I am now approaching the stage where I do not want to lend tools to "mates". You lend them a £500 sander and you have to pay £50 for a new sanding pad as soon as you get it back. They cut through a cable, put a connector block on it covered with electrian's tape, and you have to pay £20 for a new plug it lead.
As time goes on, there are only about 4 tradesmen mates that I would be willing to lend tools to. They are the kind of people that buy decent tools and understand how much good tools cost (and look after them accordingly). Additionally they understand the concept of wear and tear.
Granted, a couple of dots of paint on scaffolding boards doesn't seem like a big deal but if you lent someone your car and they gave it back to you looking like it had been used to ram raid the local branch of Dixons, would you simply shrug and say "fair enough"?