I used the same process for setting my rents this time as I did before: I checked rentometer and craigslist, then set the rents at the average for the rental size and location.

If you will be in this dinosaur sized niche, shows will not be of help to you.

If I knew the size of the units and county that the property is in I could give you a better answer.

Remember even if your cash flow decreases with your lower rent , a portion of your mortgage is getting paid off by the rent money and your equity in the property and wealth are increasing every month you get that check.

If there is a flat section of the roof of any significant size, there absolutely could be 8 layers of roofing material.

it was built in 1990 and it a medium size ranch style. 

Also, it depends on the size of the loan.

Also it may be a hard pill to swallow when you have to give a large portion of your saved/earned commission to your broker, especially when its your own deal.

Not sure how much you need monthly to quit the rat race, but a building that size for a relatively newbie investor will probably make you broke or hate life without the experience to back it up.

You could expect to see 25-35% returns on your money in a couple of months depending on the size and area for the project.