Having similar problems, only the house I want to place on the lot I didn't build. I'm trying to place one from the community library. I tried your idea "Go into Build/Buy mode" from there went to gallery, then community and lots and it won't let me place the house on my lot. I thought maybe I had to add it to my library first, then I would be able to place it on my lot. STILL DID NOT WORK. So no.. you're 'You have to be in Build or Buy Mode' doesn't work. Still needing help.
Just thought of something, maybe it's only possible in edit community mode.. is there an edit community mode? Maybe I should keep checking the forums for help.
