They also have their own construction company, property management company and brokerage under roof. 

As an example, if you have a house that has a good foundation, new roof, good HVAC, nice kitchen, and nice bathrooms, you're going to pay a lot less per square foot than if you need to replace or repair those big ticket items.

The fan can go out the side wall as well which is easier than going thru the roof. 

I'd factor in another 10% to cover roof's, water heaters, paint jobs and HVAC.

But if the roof implodes 20 years early (won't happen, but just for fun) I won't be scrambling around for money.

Note down the last time major things were replaced (furnaces, water heaters, roofs, etc.) and get them all tuned up, if not replaced, prior to renting out.

I work for a Fortune 500 company so departing will take away dinner and roof at night. 

The worst I saw at a meeting was a couple who was trying to get their roof replaced, but the only approved materials were above the price range they could afford at the moment, and their roof was leaking badly, and was past the point of them being able to get it patched.

I am about to buy 3 free and clear and want to put roofs on 2.

Need the age, construction style, updates if over 30 years old, roof type, square footage and brush zone to give you an educated guess.