Do HO’s normally leave a tip?

That’s a good question re getting paid for a sit on this site. I’d also like to know. I was offered to be paid once for doing a local house sit and declined as I thought it would be unethical to accept money as a sitter belonging to THS. I also declined the sit. Perhaps one of the THS members can answer this. Are sitters allowed to accept payment as a member of THS if they are offered payment?