You pay gralats for one, get to choose a fixed layout, you can buy furniture to populate it, and also pets (using this word for a catch all that includes bugs).

Previously on PC Graal Classic, there was a thing called the Warptex which would pretty much be submit your own levels and be able to warp to it. Before that devs would just put your house somewhere on the map (or some other map), and quality standards for that got higher over time.