Effectively offering more than 100% financing.  

Your referencing effective age vs chronological age. 

Sub2 is a risky strategy for a long term buy and hold as the longer the deal structure stays in place, the higher the chance that issues will arise (like issues with the loan servicer, insurance, seller filing for bankruptcy, seller dying, seller realizing their DTI ratio and ability to buy their next property is negatively effected and becoming upset about it like in your case, due on sale clause being called, etc.).

I have checked with our lender and keeping this home's mortgage will not effect qualifying for our next house.4.

If you do the math, since your borrower is paying interest on interest, it raises your effective interest rate by about a point.

Prior to last year, effectively any SFR was eligible for a short term rental license.

They don't understand how to price effectively, study the market, set boundaries with tenants, establish policies and procedures, communicate, and dozens of other things.

As a rental strategy for non owner occupants, it absolutely is a fantastic way to generate the highest return, that's true.....but also, and most importantly, your screening has to be on point, and without that, it won't be as effective because one bad roommate can ruin the environment for the other roommate tenants. 

These are people whose full time job is to effectively manage the assets on behalf of the investors. 

The PMS around here are pretty terrible, I've worked with a lot of the larger ones in Cleveland and I think they just take on more properties than they can effectively handle and don't hire enough additional employees to make it work.