Ugh I am the literal worst at recs because my memory is just awful.
But I can highly recommend Special Delivery by my friends Merkat (merindab and themadkatter13). Also, Distractions by anigrrrl2 even though that doesn’t fit either the rentboy/prostitute thing …. or Sherlock being the glittery one (seriously though John is super pretty and wearing tiny shorts and it is worth your time).
I’m not sure that there are all that many rentboy or prostitute Sherlock fics, or at least not that I’ve found yet!
Maybe ask kinklock if she has any recs! She doesn’t have a rentboy section yet, but perhaps it is forthcoming.
My fic Ilium is prostitue!John. I’m on mobile but http://archiveofourown.org/works/1084877
