In my area you have to strip the roof shingles at a minimum . 

Do you save three months of vacancy for each unit and $50,000 for the roof replacement?

And if all houses have not been fully rehabbed (we do fulls on every buy), some expected number for capital expenses should be included in that (IE if you have 3 years left on your roof you need to be deducting $X from that figure, repeat ad nauseum for all major capex).

Our biggest climate risks in central Texas are typically wind and hail, so anything of concern regarding the roof could get an applicant declined including trees too close to the roof surface, roof over 10 years old, etc.

I hope you or someone is at least keeping an eye on your properties for break ins, squatters, roof leaks, temperature control, frozen pipes (if in cold climate), if you have a basement and sump pump goes out leading to water damage etc.I just talked to two investors in California that have let their properties sit vacant (no mortgages so paying property taxes and insurance).

A roof on the 600K property will cost more than on the 300K property, but you have more roofs to repair on the multiple 300K properties.

You have the mortgage, taxes, insurance, maintenance, capital expenditures (roof, flooring, etc.), and also need to consider the cost of vacancies or bad tenants.I also recommend you charge market rate, for yourself and the tenant.

Large basement and attic space, new roof and some of the kitchen is already torn out from the current owner. one bedroom does have a closet that will need built. plumbing seems fine, maybe a couple angle stops to change.

I know the 401 penalties are steep but my thoughts are if I can gain enough cash flow to leave my current career, do I really need to worry about whatever money is in there to draw from 20 years down the road?

Or just avoid ST booking platforms.2) Converting the roof into a terrace (apt. on the top floor).