I would make them buy land. And, you may say that they already buy land for their houses, no, what I mean is make them buy a small field then, they would build their house on the said field with what we supply (we would over-charge them), once they more settlers start coming, we would tell the original settlers that we would have to cut their land for more settlers. Then, we would cut land, and pay them a pretty small fee. And then we keep repeating this process with future settlers. And then maybe we could buy more land and repeat the process of this.