There are a few types of buildings in Castleville Legends.

Firstly, there are the Royal Buildings, which are more or less given to you. You may need to click a few things, explore to a certain piece of land, or wait a little while, but the buildings themselves are basically free.

Next are the Workshops. These are buildings you purchase, and which only become available for purchase at a certain level. These are the buildings that you use to craft the various items needed for your quests and explorations in the game.

Just as in the original Castleville, there are characters' houses for each of the game's characters. Rather than collecting "taxes" from them, however, in Legends, most of them produce useful items. For example, Yvette's house produces opals.

Finally, there are the Places of Legend. As with the royal buildings, these are fixed in location, and must be explored to in order to get them. While they are free once you reach them, the exploration costs can be significant, and there are always level restrictions on how soon you can explore to them and their surrounding plots of land.

Castleville Legends Wiki