Their tenant helps cover the mortgage.

He will not be able to properly execute any skilled trades without exposing yourself to tremendous liability.

Maybe  DSCR 2nd if both the 1st and 2nd mortgages meet the debt service requirements. 

The mortgage is 8 years in

They are unable to qualify for a mortgage currently as they are out of work so I am stepping in to help.

The most obvious is that you will be able to offset your mortgage with renting out a few rooms.

In my experience, Banks make it really difficult to obtain a mortgage and I have never been able to succeed in obtaining a loan with them for investment purposes simply because they require a certain amount of DTI ratios.

-A property with a 30 year mortgage would be neutral cash flowing, but in a solid location and with strong demand. 

Or maybe a subject to if they have a decent-sized first mortgage?

The CoC is great and we don't have a mortgage on the condo, however the current market value of the condo is about ~200k, so very less appreciation in last 10 yrs.Should I sell the condo and invest ~200k (minus fees) to buy an investment property with 30-40% down in an area (Durham, Raleigh) where I could expect greater appreciation down the road.