Get (business) married - form an LLC for long-term partnerships. there are various blends of this

Backup plan was to retain as rental while paying down note and long play on appreciation, hedging against inflation.

Purchase price: $430,000 Short Term Rental

I would not invest if the good guys are losing ground, but that would run counter to your description that it is an appreciating area.It looks fine to invest in for the information you shared if the long term forecast for the area is safe and stable to improving.

I think the answer to this question really depends on a few factors such as your current unit count, location of your properties, long term goals, and how much of your income is based off of your units. 

And also keep a nice chunk of change in reserves or very safe short term investments.

Or even the benefits/cons of that relationship being long term?

In terms of getting into apartment complexes and large transactions - it's much easier than you think.Real estate is filled with opportunities to deploy capital, but in the same time is filled with fast-talking snake oil men that will happily take your money towards a "fund" so you own a portion of a large portfolio... only to find out the fund's performance is below par, your money is locked out, and the only person making money is the fund manager from the management fee they've locked you into. 

Hope this will result in a longer term stay with eac rental.

Be sure to check local regulations regarding short-term rentals as well.