I never said anything about blind trust. Life and businss is all about systems. You need systems for your accountant, for your bookeeper, for your contractor, and for anyone who controls any part of your business.
A lot of contractors get into the business by default of they weren't qualified to do anything else. This gives the whole industry a bad reputation.
However, there are a lot of people who are extremely talented and truly love building.
If you insist on buying your own materials, and micro-managing your contractor you are severely limiting your opportunities for growth.
Treat your contractor like a member of your team. Trust has to be earned, and put systems in place that control and track expenses. But one house you micro-manage equals at least 4 houses your team could manage. Do the math.
I have had contractors save my butt on more than one occasion because I have a good team.
Beyond that, the fact that you wrote the check for the materials doesn't mean your contractor, or one of his guys can't steal them. Possession is 9/10ths of the law and you'll face the same battle either way.
The position I take is the contractor is responsible for the entire job untill it is signed off. If stuff goes missing, it's on him to replace.
In the future I may make a specific post about evaluating and hiring contractors. Like anything, experience goes a long way.