If you mean for a rehab, definitely consider National Real Estate Insurance Group as they let you add/remove properties on a monthly basis and don't bother you with inspections.

(Let’s say if we require 100 doors via multi family apartments)Is it like an 8 to 16 hour job every day like I’m doing now?

For what its worth most deals I deem meeting minimal IRR standards is 13-15% but you have to dig a little deeper to uncover the real placements of cashflows and capitalization events... and then dig even deeper to verify the assumptions such as occupancy, rent increases per year, and what reversion cap rate was used.Again I don't look for IRR cause its manipulated a lot instead I look at total return on a 5 year basis.

An addition would most likely be considered an improvement, not a repair/maintenance, so you'd probably just add it to the property's cost basis. 

Thus, on a monthly basis, this is about $1,900 of revenue out of a $750 rental.The other unit we have is clearing about the same.We will have about $300 in costs associated with each of these units, thus the Net is about $1,500 - $1,600.

However in this case your basis in the property would be 0, so in the future if you were to sell you would pick up the entire tax burden.

There's 24 hrs in everyday.

Many of the regs concerning OZs were rolled out on an on going basis. 

Run across this pretty much EVERY DAY in my wholesale business.

I only say this because if your mom plans on passing the house down to you in her will, that would be more beneficial, as you would get a stepped up basis on the home, as opposed to paying for it on the market.Happy to chat further if you want.