Consider vacancy rates and look at the historical appreciation of rent in the area.In Canada very few markets support good cash flow comparable to the United States, but we still have thousands of very successful investors who make due in every market.Do what's best for your future.

The cost to replace will depend on whether those are still structurally sound enough to sister in new joists ( basic labor job plus lumber ) or if they are crumbling and need to be removed to be replaced ( major job, skilled labor, temporary supports, remove and replace ).

Also they tend to be quieter, not throw loud parties or have too many people over, or cause a lot of wear and tear on the house.You can't advertise specifically for "older couples only". 

Some lenders look at cash flow to make sure the income can support the debt and will probably want you to have a experienced property manger managing.

For me, I would never consider a partner that was not adding equal money.All of this assume the comps in the area support the total build costs (land plus construction).

You don't find private lenders by advertising. 

My focus now is upper middle class areas that support rental units.

They started out way high.The area and house won't support nearly 80k.

If you have a title company that is investor-focused (or supportive), and owned by an attorney (or at least has good relationships with a law office) then you should have a helpful guide to generate the debt instruments needed. 

Someone advertises how should I spend my $50K and magically three or four people have a great way to give them double digit returns.