We built it over 14 months. Did a lot of the work as well with, contracted out for Electrical, plumbing, and foundation.
I wanted to save some $$$ and it did work well as our total Loan when we moved in was 117K but the home estimated value was 170k+ for everything so we walked in the home with close to 55k in equity. When everything tanked we dropped as low as 19k in equity but never went upside down.
It was a huge blessing for us, but to be honest I will never do it again. I gained a lot of grey hair and aged more than 14 months doing it. Though, gained some amazing friends along the way.