My wife every now and again will give me sex in exchange for money. Its more a game she'll play, because she has control of our finances anyway, but if she sees an expensive pair of heels, handbag, dress etc. she will offer me 'hotwife' sex for money, so i put it on my credit card and not hers.
Depending on what I pay, depends on what I receive, but usually it might be the lingerie/ heels she only wears for our bull, as well as wear her particular 'hotwife' perfume that she only wears for when playing (that drives me wild) Extras are if she has her pussy waxed, if i'll pay to go bareback, she evens charges me extra to wear her anklet.
Unfortunately its only offered when she desires or needs something, and I only get to purchase what she offers. It is a lot of fun though.