@Stephon Mosby Williams call a few lenders. Ask how they calculate for the unit you will vacate. You were 2/3 occupied with $0 profit, that means when you move out unit #3 is all profit and should make you look like a rock star. Most will calculate 75% of the lease, but since you don't have one they may do 75% of "market rate". If your other 2 are like the third, you can argue market rate pretty easily.
Similar tact for the new property. How do they calculate the rent income? It should also make you look good. There shouldn't be any hangups. FWIW, you have an FHA hanging out in the wings, which is pretty good for landlords and calculation of income, though you have to refinance out of the mortgage insurance if you didn't do 20% down at the start.
I honestly wouldn't mess around yet with all the "go get a commercial loan" type advice. Locking in an amazing, non-adjustable rate for 30 years right now is a no-brainer unless you have compelling reasons not to.