Negative aspects of work by the general contractor
The first minus is time. If you are a general contractor, then you will have to spend a lot of time before it starts. You will need to find subcontractors for construction and get estimates from them for work performed. You should also agree on the final cost and on the schedule of work. And this is without the fact that you will have to do financing. On average, for such training, it takes a whole month and all your free evenings, and weekends.
The second minus is the responsibility that you put on your shoulders. The entire budget intended for construction work depends only on you. If you do not take into account something or forget about the cost of the work of this or that type, it will only be your problems, and you will be responsible to bear responsibility yourself.