I'm a contractor and I've built a few houses. I don't like building houses, so I mostly do remodels, repairs and finish off jobs that other contractors disappear from. In my opinion, when a home owner does their own work, or is the GC, they either do a really good job, or a horrible job. Since it's their home, their attention to detail is often a lot better then you would expect from a GC. Other times, it's so bad that you just have to tear things apart and start over. In my opinion, the big difference is in knowing how it is supposed to be done, and not accepting "good enough" or "that's how we always do it" or "the other guy does that" or "its code" The "its code" one is probably the most common when not wanting to do something. The other thing is in every case when things are going badly, the client always knows that there are problems, but they keep hoping it will get better. It never does. Once you start to run into problems, stop and find out the correct solution. If you know what you want, and you are comfortable dealing with people that may not be honest with you, or not actually skilled in what they claim to be experts at doing, you should be fine.