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

You could also use a process server, but I like sending someone with a gun and a badge to put a little fear into people.

I was in the middle of a BP Real Estate Podcast and it just stopped. Listening on Spotify, tried the next episode no dice, switched to iTunes, still no dice. Then I tried the Business podcast and it appears to be down...

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 am currently 21 years old and taking time off of college and working full time as a server. 

Or if they are a stripper, drug dealer, or server they could be getting paid in cash.

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.