A pool for a house and a gang house?
Why not buy a pool and be able to put it in your house? It will be a good thing to have at party's or other celebrations someone might host.
Types and price-
You could have various types of sizes of pools; the bigger pools cost more and the smaller pools cost least. Maybe different sizes like a oval or a square, etc.
Add-on's
You can have different things you add to the pool like a floating toy or whatever pools have. Maybe you can get a dive board and dive off of it.
Surroundings-
Maybe like little pool tables and pool chairs, cooler, a umbrella, or a grill; to spice things up.
This is my idea,
Sincerely, Sierra*