The owner at the time spiraled into dimentia, and his son wanted a quick sell to help pay for his home care.

The only thing was, got a break from the seller when on purchase, prices went up like crazy, so after 15 years, 1031 the property into another.Talking about tenants in their 70's, I looked at a property here some years back, rent controlled, tenant is paying $98.00/month on a unit where the market rent was $800.00, and the tenant at the time was 90.

Property B Assume the loan with 4-5% interest rate, pay difference in equity $70k and pocket 300-400 in cash flow every month.

And if the amount isn't too large they can either keep the note outside the exchange and pay some tax on it as boot doing a partial 1031 exchange. 

With conventional, you can just drop the MI when you have the equity- you might have to pay a few hundred bucks for an appraisal. 

Do they take care of the place, pay rent on time, etc? 

However, you pay for it.

They argue that their renovation is top notch, so the price is justified, which may or may not be true, but but generally the high quality of the renovation does not pay sufficient dividends in the form of increased rent, so the price to rent ratio just isn't there.They typically advertise a 9% to 13% cash on cash return, but be careful, this is their "first year projection" and in their first year they do some things that I find a it deceptive, such as not accounting for vacancy because they place a tenant prior to closing, and they budget essentially nothing for repairs or cap ex since it is renovated and they offer a warranty. 

@Travis Biziorek how much did you pay for the duplex example?

This trend is expected to persist, driven by Birmingham's affordability and favorable living conditions.