I think it would be worthwhile so you have at least foundational understanding of the alternative decision people are making by leaving massive amounts of equity on the table in exchange for the convenience, control and speed of an off market transaction.

While I haven't had to deal with this myself, I think the best thing to do would be to help them as much as you can by giving them a nice letter stating what a good tenant they were(if they indeed were a good tenant), or alternatively, you could at the very least try to send them on their way with direction towards a new rental.

Alternative, my options might be to buy an existing mobile home park? 

I had two stellar deals fall in my lap and I wasn't educated enough with alternative financing to put it together. 

But there are these massive space heaters inside each unit that I think do use up a lot of energy so maybe I’ll look into an alternative heat source.

So until you have an insane REI portfolio go buy gold or silver if your looking to park your money in an alternative investment to diversify your portfolio.

Is there a way to circumvent the employment history in order to obtain conventional financing (besides getting a co-signer), or should I start contemplating alternative ways to finance my investment?

There's a good book in the BiggerPockets library that's specifically about alternative methods of funding investments.

Alternatively I have considered purchasing an apartment in the expensive market and BRRRRing it so that I could borrow against it to buy a house in the future.

Alternatively would it be better to pay up to 20% of the FHA loan in order to refinance into a conventional loan and then the second property use an FHA loan.