It had an offer of 269k a few months ago, I decided not to sell since the a new house is more expensive and high in demand for my price range.

Whats the highest price range you could go up to and still qualify for a low interest loan?

I see a lot of new investors looking at these 50-80k properties and those are much harder to find lenders for than even the 80-100k range. 

@Michael Baum I would like to be in the mid 300 range.

Allowing her to pay it over a specified range of time is fair but yet is upholding the lease agreement to the letter, which is what you should be doing.

As someone mentioned, cap rate is a quick way to understand a property and determine if it's in range, but there are several more factors to determine whether the property is a good investment or not.  

Their house price range is 1.5-1.8 mil in McLean/Langley/Marshall high.

I do see opportunities listed at lower price points, in my opinion most on the lower-end tend to be overpriced for location and condition, because there just aren't many listed for sale in that range.

@Marco MorkousIt's not used too often because it makes the house less desirable to buyers, but it is basically a contingency for the seller to find a suitable replacement home ranging from 30-60 days. 

The total package is the in the $400k range and single family homes in good condition in the area are selling in the $180k range.