I have written about this topic a lot, because its an often confusing and tiring conversation for most.

The facts are easy thought;

If you want to be hands on and very involved (i.e. reviewing paperwork, interviewing trades, selecting materials, etc) then you shouldn't hire a GC.
You are the GC. If you are concerned about someone overseeing the project (super) or making sure your pricing is right (estimator) then you can hire those things out; like a GC does. 

Its never advisable to hire a contractor and just walk away hoping things get done. Visit regularly, or hire someone who will. You can hire inspectors (like the ones who look before you buy) who will do "phased inspections" at certain parts of the project. (before inspections of dirt work i.e. ground cover inspection, rough plumbing/electrical, framing/structural, HVAC, and so on. To not only make sure that it will pass, but to insure that you get better than a basic city/county inspection. Just remember that being an investor doesn't mean "cheap".

Individuals, REIT's, PM companies, and even local governments have hired me as a consultant to provide fact-based info on projects for years. I can tell you that its not easy to find pro's to work with. I will also tell you that proclaiming "Im an investor" when you are early in the game will only chase away the real pros, or leave you jumping through way more hoops than need be.

Not everyone likes to pay people to do things like I do, and I totally get that. I can paint a house and install tile (started as a Handy Man 20+yrs ago) but I still hire that out, and pay well for it. I know that hiring the guy/girl who does something day in and day out is way better than me at it, and can save me time/money/frustrations. I just figure into ever project I do as an investor what it will cost to have me do nothing. Again, hiring someone to do everything including the inspections. The reason is simple. I can do everything, but I am an investor; not a handy man or contractor or superintendent. Sure, I do my own inspections, but what if something happens and I can't. Then I don't get "extra" money, I am losing my profits.  

Note- Broke my wrist once and had to hire out all the little stuff I was going to do to make the project a deal. I wound up making 4k and paid out 12k in the "little stuff" I was going to do. Made me realize, my numbers were emotional and incomplete when I did them for myself. Since then I don't assume anything other than the project will need someone else to do everything.  Plus..it allows me to one day step out completely and pay someone to do the few things I still do.

Good money = Good work = Good project = Good profits.