Folks in professions like yours need to talk to your unions, or whatever, and get pay raises in exchange for the per diem being reduced. 

We held onto it for a few years a did a like kind exchange (bought up), into a newer, larger, more expensive property.

Simple way to think of it is with the additional principle, would you rather invest it and make "x" (x being whatever return you can generate through RE, stock..etc) or use it to minimize the 3-4% interest rate that's locked.

I have a few people in mind who I would like to ask to be a mentor, but I want to find a way to bring them value in exchange for their time and energy.

I've been very busy for the last couple of years, and am sinking almost everything into this, including emergency fund and all my "play" stocks. 

This article isn't answering your exact question, but it brings up a lot of the perks of owning a rental property versus investing in stocks.

So I would say take a look at the housing stock mix of your home town and then adapt accordingly.   

Just wondering if anyone would like to meet up and exchange some real estate knowledge.

Got that done at least,  but the sale I planned for this year now has to be delayed again or 1031 exchanged. 

The best returns you get are inevitably going to come from the stock market but real estate has the added benefit of allowing leverage.