Right, but you could get a parcel of land that‘s very small, or steep, or otherwise unusable for normal homes. Depending on local regulation, you also might not need a building permit, or there might be a simplified procedure since it is very small and/or temporary. (For example we have a lot of „green land“ in Austria, where you are not allowed to build. For this reason it is very cheap. But you can of course erect a tent on „green land“.)