Actually, think better, that's the thing:
1.The richest and fanciest house in Bikini Bottom is Squidward's Tiki, as it is magnificent and wonderful, with creative architecture and appeals more to aristocrats.
2.Undeniably, Patrick owns the plainest, the simplest house of all, as it is just a rock (with an antenna on it!)
3.Since Sandy apart from athletic is also a kind of scientist lives in the most sophisticated place in Bikini Bottom, as her treedome is a scientific result, with hard work behind it.