For the record, I always just considered Greedo to be a 2nd rate bounty hunter. Hell, maybe he's a 3rd rate bounty hunter. He likely was on Jabba's permanent payroll, but wanted to be a big shot by capturing Solo. He wanted something to gloat about.
Why Boba Fett is lurking around the palace in ROTJ? Not sure. Maybe Jabba put him on the payroll as protection, but Fett's an expensive professional. From whom would Jabba be afraid of coming after him in his own palace to employ Boba Fett at such a high cost. I'm sure the Hutt's got the money, but that's not the point. Fett's not the type to just hang around out of luxury.
-NJM