Rich is right. For me, the sewer hookup was a big questionmark. I got lucky, and the city let me tie the sewer into the house. But for that, I'd have had to dig a 7-10' trench all the way around the house! That saved me thousands. I'd hoped that my poolhouse would cost about $20k, but I was prepared for it to be more like $30-50k, and it looks like it'll be on the high end. I've made adjustments, though, that have added to the cost for sure. If you really kept it small and didn't deviate from the plan, it would be easier to stay in bounds. Let me add, though, that every time I look outside, I'm SO GLAD we went ahead and started the poolhouse at the same time as the pool which the backyard is already torn up. Access to a toilet from the pool was otherwise going to be a real issue.