If I understand the story correctly, unless your jurisdiction says differently, these are your tenants and if they don't turn the property over to you, you will need to seek an attorney's assistance in evicting them both. 

Don't concern yourself with the increase over time , you will only set your self up for dissapointment .3.

Of course, I do feel some self-pressure to find something, but I realize the fundamentals education alone is probably 6 months to a year.  

She self manages her and her husband's rental portfolio from wherever in the world he's currently stationed on AD. 

A good Realtor should know your particular market inside and out, help you analyze the cost effectiveness of buying certain properties and assist you in offer negotiations while guiding you through the entire REI process.

I would however assist the present owner in removing the tennat.

Other people may be able to go higher because they have different strategies like self-performing more of the work, or plan to live in it.

The additional time it would take to self manage a 4 unit portfolio over a 2 unit portfolio is non consequential.

However, we only have about 7k saved up, and would prefer not to have to use all of that on buying a house so we would probably have to leverage a first home buyers type loan and maybe a down payment assistance type loan.

@Rachel H. well just real briefly, I plan on having a self sustaining source of income in rental properties to the point where if I wanted to leave active duty I can and be able to manage and Persue other investing full time.