It's hard to put an exact amount on it given property values vary so much and there are a bunch of other factors to consider. 

Anything 1-4 units is valued off the sales comp approach, so no, income does not factor in.

You do have to "kiss a lot of frogs" to find the right tenant, but just factor that in. 

When you factor in the tax deduction you get on the mortgage interest, this 5% rate on a CD closes matches what you would save on interest by paying down the mortgage.

Time was a factor as the bank was set to take the property back and we had pushed the closing back one day before it became REO.

Hi Joseph -  For your first scenario, if you acquire another SFH with a traditional investment loan, the rental income can count toward lowering your DTI, but typically only a portion of it (usually 75% of the rental income is factored in).

That is another factor to see if it's worth rehabbing the property.

This is by far the most important factor in my opinion.

Also, what key factors are influencing your decisions?

Consider factors like retirement, landlord fatigue, property maintenance issues, or asset liquidation.