That seems like a fun idea tbh. I mean i wanna say the houses themselves should be different types.
1. 600k is like the cheapest house. Decently big, just plain.
2. 900k- Big, upstairs and downstairs with a pokecenter.
3. 1.1 million- Very Big, Upstairs and Down Stairs, Pokecenter, Shop, Is in every Region.
Also you have to buy your own furniture.
This is just ideas off the top of my head rn but guild houses seem like a very good idea and just very fun to have in general.