I grew up in the area (Maryland) and attended school in state before moving up to NYC and then SF for work in professional services (consulting, strategy) and technology.

NOI is $13151, which would be an 8.2 cap (this is a 12 cap neighborhood), and debt service would be 6400 with a 30 year am, 5% interest.

Look no further than maps with traffic, ride sharing, online booking services, even agriculture adjusting fertilizer in every square foot of the field to match the soil needs. 

I am also a former US Marine and separated from service in Hawaii where I lived for 10 years.  

I'm on the rental services commission and I'm frequently going back to review new legislation to ensure we're doing things correctly.

I would not keep him at $485 but I would sit down with him and tell him the other tenants were paying $200+/month more and he needed to pay at least a bit more in rent or services each year.Maybe go up $30/year and get him to help out with some more maintenance tasks or something.

Frame it as a service to them - ask if anything needs repair/rehab. 

It's more likely that people reading this would decide against using your services.  

@Walter Correia, You're going to see a range based on service level, economies of scale and geography. 

That all depends on if the rent will fully cover mortgage, tax, insurance, 5% of rental income for repairs, another 5% for CAPEX, another 5% for vacancies, and another 10% for PM services (even if you self-manage).