I am based in PG county Maryland. 

One of which is trainers utilizing my space and pay me rent for time slots to teach classes.

Hello, my husband and I are handling our first major rehab, which includes popping the top on a small SFH to add a second level, and digging out the basement to create additional living space. The basement dig involve...

That said, you will need to refinance off FHA to clear your 1 FHA slot to then do the new purchase with FHA again. 

I would caution from using a PG without really understanding her net worth or income potential.

@Kelly Jones    This is the source.  2021 Publication 527 (irs.gov) pg 15.   

IMHO it's more important to take action on the "how's" than spend too much time tracking 5 different metrics or spending too much time analyzing goals or creating even more that likely won't get done.Another great tip-- put EVERYTHING on your calendar so you have specific time slots for all the "how's" you need to get done and stick to them.

No more investors can step in at that point on the other units if they want to use a loan to purchase.Maybe I'm worrying too much about it since, if I own a unit as an investor, and I want to sell to another investor, they can still purchase it because they can just take my "slot" as one of the investor units.How much does that situation dissuade investors, if at all?

If it's not police sirens, it's helicopters, or neighbors dogs, or kids, or planes, or slot machines lol.

You can always refinance your investment properties later to "free up" slots if that becomes an issue for you.Once you moved out of your primary, it became an investment.