In the rental agreement it clearly states that the rented portion is just one bedroom with a shared bathroom.

In the rental agreement it clearly states that the rented portion is just one bedroom with a shared bathroom.

Consider more than just rental income, such as, prior tenant history, civil and criminal background, employment history, number of occupants for the size of the home, desired move-in/move-out date, etc.

In the rental agreement it clearly states that the rented portion is just one bedroom with a shared bathroom.

I recommend a structural engineer further evaluate and make recommendations related to this observation” And regarding this make-shift supports: “Temporary posts exist in the basement that should be considered for replacement with a permanent support system.A temporary post is noted as a support to the ground that does not appear to be resting on a footer.This temporary support post is holding up a metal beam supporting a large portion of the house.This is a structural concern that should be reviewed by a qualified engineer/contractor”I will include a couple pics as well 

You can use a portion for private lending, and for the balance, you have thousands of other investment options.

Her sister still lives in the house with a roommate so my wife's portion is covered.

The proper way to approach this appraisal problem is (summarized below):* find reasonably similar comps - find relatively recent duplex sales in the Subject's market area and adjust for differences, based on market response (i.e. how much more/less buyers would typically pay for certain characteristics like size of units and lot, location, quality/condition, etc).* In the absence of similar comps - go back in time to find any similar comps, no matter how long ago and adjust for market trend differences (appreciation, etc), as well as other adjustments as typical (size, bed/bath, condition/quality, location, etc).* Go to nearby market areas/neighborhoods and find reasonably similar duplex sales and adjust for market area/neighborhood differences as required - along with the other adjustments.* Find reasonable 3 or 4 unit (not more than 4, and they can use sfr's, but those are typically not as good for comparison.

If 75%*rent is less than PITI then that difference would be added to the top portion of the DTI calc. 

The lot with the house on it sells for $550-900k depending on location, house size, etc.