No guarantees even if you supervise the building. Bought land some time back (which has appreciated tenfold). Interviewed several builders and of course picked the wrong one. Eventually kicked him off the site (I'm sure his back pocket was bulging). Got another builder who first had to correct the cock-ups the first builder made, including replacing the whole roof. Cost a small fortune but I accept that mistakes are expensive.
I was on site every day and still I got it wrong. We have a very nice house now but there were many problems encountered during the build.
At the end of the day, if you dont have the time to be onsite 24/7 it's best to leave the problems with a developer. If he has a problem then at least it's at his cost.