When you want a larger house, you can go see the carpenter (大工のおじいさん,Daiku no ojī-san? lit. Grandpa Carpenter). He will build you a larger house if you have enough money and wood material. It is hard to get enough wood to fulfill the material requirement, but the carpenter also sells extra material for 10G a piece in groups of 50. Here is what he has available in his store:
