When I'm setting up my rental units, it actually varies, as if I get an idea for the sim(s) I want to live there, I'll deck it out fully with furniture and everything for them. If I don't have a sim planned, I'll just do fixtures (kitchen/bathroom cabinets, lights, appliances) and figure it out later.
My one exception so far has been the Long Term Resident Motel I build on the Old Penelope Lot, because that's supposed to look like a cheap Motel. I'll probably do the same for the "hotel" I plan to put in Del Sol Valley.
Of course, I have zero plans to actually play as a landlord at any point. The closest I plan to get is to motherlode the Landgraabs a few times and have them buy the lot so I can set up rules for buildings I want to have rules. I just want a few more options to have sim households living in world (as opposed to pretending they're living in the shell houses.)
For the gallery, I prefer to do fixtures only, so that it's a nice mostly blank canvas for others to use.
