I do loads for friends and family, rarely is payment made or offered, I always have a rider......... (a list of demands, commonly used by pop stars when doing a gig).
My riders have varied from cream and scones, at my mothers house, to a pair of jeans, at a friends house, to sexual favours, er that was at my house , in about 1998 while I was still married. My advice is to always ask for something, even jokingly, however wierd, I recently asked for 4 slices of cheese on toast from someone who could not afford a clean. Doing this creates some kind of value to your service and a talking point so the people who you cleaned for tell others who do pay, plus I am of the opinion that I have a responsibility to help others.