Price growth and population growth have gone hand-in-hand the last two decades so at this point, supply and demand are no longer in sync and that has contributed to high prices just about everywhere in the US.

The commercial lender will be more concerned about the property's ability to cover the mortgage payment (they look at it more like a business) than they look at the debt-to-income ratio.

You have the ability to accept or decline anything at any point.

That would give you the ability to full rent out your property #1 too. 

I believe La Pine is in the path of growth for the Bend area and prices here were 100k-200k less for comparable homes.

@Edward C.Northern suburbs seem to be doing well (Cedar Park, Round Rock), but given the amount of growth there coupled with low inventory it makes sense.  

Columbus is a top five appreciating city in the US with an unexpected mix of cash flow which is backed up by a population and job growth.

The options I have would be to go in alone and get a duplex to at least get started and have the ability to rent out the other side.

Some investors believe that it might negatively affect their ability to borrow.

All markets you list will still be cities with populations forever, and your exit will be to a resident in that market, so population growth/decline, employment drivers, etc are of less concern relative to a large, institutional sized apartment complex.