And lastly, I search FunishedFinder listings nearby, find comparable properties, and track the listed rent for a few months (does it increase, decrease?).

The entire lots level has to be increased.

The mortgage has gotten out of hand due to property tax increases, miscalculated escrow, and an increase in my interest rate from an initial buy down, increasing from $2600/mo to $3200/mo.

When you mentioned that you don't have a lot of money to start with, I'd recommend focusing on increasing your current income and decreasing expenses.

It's usually better to earn $200 less a month for one year than to sit vacant for two months, particularly in the winter.Consider a bigger drop for a 6-month lease to get through winter, then increase rent or find a new renter in the spring when competition is hotter.

I agree with @Jonathan Greene that the question is vague, so my advice will have to be as well.The short answer: MTRs are real estate, so just like all real estate, any place that can long-term-rent cash flow with increasing jobs/population can be a suitable site to purchase. 

I’d recommend looking for properties that already have stable tenants or need minor updates to increase rents down the line.

The home has been doing okay Occupancy wise it is following the same occupancy as the average occupancy in the area so around 60-77%  but it is a new unit, this march it has increased to an 81% occupancy and April and May its picking up in occupancy fast so its a perfect time that I started this airbnb. 

And the Idea of true wealth in rentals I paid for over time.. your tenants are paying your mortgage and increasing your net worth monthly. 

When cap rates increase you have to have an impact on NOI great enough to overcome the cap rate adjustment plus a profit.