I would also check references and make sure the installer is licensed and insured.Roofing has more variables-disappointments- than even plumbing and you want it done right the first time.

Check back soon for more adventures in investing.

Alex, check the forums for agents in Baltimore here.

I would check it out with your planning dept.

Someone else had posted the same comment a long time ago, it would be worth checking it out to give you an idea.  

Go check those areas out back in the 90s.

And/or assume that everything is trashed and you have to rehab the entire house.I have bought houses without going inside, but you can usually get on the property and look in some windows. check the roof, exterior siding, main panel, etc and get a pretty good idea of what the house will need.

Check into their BBB rating and real reviews.

I'd recommend checking out some turnkey property managers to get a sense of the numbers. 

I'd check both of these.