@McKenna Garcia Congrats on your first post. If you can find the courage to ask a lot of questions, BiggerPockets will be your very best resource for valuable content at no cost to you.
Fannie Mae is who insures FHA loans in case the borrower defaults on the loan, meaning the Federal Housing Administration (FHA) will cover the loss of the loan lessening the risk for the lender. As the old idiom goes, "He who pays the piper calls the tune." I.e. The FHA backs the loan and pays on the loss if the borrower defaults, so the FHA gets to make the rules (Guidelines). These are what your lender will have to use to make sure each borrower falls within in order to "Qualify" them for the loan.
The FHA changed existing guidelines in January of 2019. The old guideline under, "Rental Income on Retained Primary Residence," it changed from saying: "Rental income may be counted when relocating outside or reasonable commute distance for job OR borrower has 25% equity" but changed to: "Rental income may be counted when relocating and new residence is located at least 100 miles from previous residence AND If no history of rental income since the last tax filing, borrower must have 25% equity."
So, the $2,200/mo. we'd be getting in rents for the unit we are leaving would not be considered in the equation as rents received when qualifying for the new property. We will still get the rents and they will be cash-flow, but it cuts our buying power down fairly substantially.
We (and you) will still have many ways to boost your buying ability by maintaining a good debt to income (DTI) ratio and structuring your taxes each year to pay more to the Federal Government and the State, but you'll be able to show you earn more and can therefore qualify for more.
Hope this answers your questions. Happy posting and good luck in your future REI's.