to my knowledge , Squiliams house has the elevator. Squidwards house has a spiral staircase that leads to the second floor, There is also a library and art room there,.

That's weird, because in the earlier seasons, Squidward had an elevator. Later, he had a staircase. This staircase can be seen in the episode "Squid's Visit."

Squidward keeps a talking toilet in his house LOL.