Why should the thieves guild have the only people to buy stolen goods? Nobody else in all of skyrim will buy stolen goods? How would they know they were stolen anyway?

No scripts added, cleaned with tes5edit, a very simple mod.
Just Drop into your data file.

This mod will make the merchants listed below buy your stolen goods. No perks needed, right from the start of the game.

Bersi...........Riften
Birna..........Winterhold
Belethor......Whiterun
Lisbet.........Markarth
Lucan.........Riverwood
Sadri..........Windhelm
Sayma........Solitude
Solaf..........Falkreath