I see people “try” to do this all the time. In the long run, unless you know how to build a house from top to bottom on your own, trying to GC it yourself is not a good idea. All the subs will see you and your wallet coming from a mile away. 
Think of the money you save by wrenching on your own car, building a house is kinda the same. If you don’t know what you are doing, don’t try building a car from scratch.
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