Dodd-Frank specifically lists this statement as one of the five factors a lender should use when deciding whether the loan is for a business or consumer purpose.

It depends on a variety of factors, including the strength of your justice system.

The number one factor of what you buy is how much capital you have access to...that means its a combination of purchase price, location, condition, and availability of inventory...I would add these as metrics alongside the cash flow.

Another less-ideal factor is that if I buy these on one loan (as may be necessary to meet minimum deal size) then I will have them forever linked, even after I refinance, unless I pay off the loan.

There are a lot of factors, but you may need to start with a DSCR loan, which looks mostly at the amount of income from the units vs the mortgage.

Given these factors I would wager a guess of around $2300-$2500/month in rents, however with a 5 bedroom home in one of these areas it can be very possible to get that in rents without having to go to the headache of rehab.

The safe harbor provides that the IRS will not challenge the qualification of property as either replacement property or relinquished property, or the treatment of the accommodation party as the property owner under the like-kind exchange rules, if property is held in a qualified exchange accommodation arrangement (QEAA).

In general I think humane treatment comes down to intent and communication in situations like this. 

Each turn means more wear and tear repairs (not reimbursable through security deposit) so factoring in higher repairs/turnover costs could be worthwhile.  

My bank has 5 branches, a local board with people I know, and other key factors.