Advice on using an FHA in Dallas for MFH

[Michael Flood]

Hi all, over the course of the next 6 months (hopefully much sooner) I am looking to buy a personal SFH and a MFH (preferably 4-plex but will pursue anything where the math makes sense). I am leaning towards buying the MFH first and my tentative plan is below. Seeking any advice you're willing to give and am also looking to confirm that what I am proposing is legal.

1) Use FHA to buy a duplex/4-plex with a vacant unit that would conservatively break even or cash flow positive with the minimum down payment and have the 1 vacant unit that needs work.

-I currently live in an apartment with a great rate. If I use the FHA to buy a MFH, would I need to break my lease and physically live in the currently vacant unit of the MFH? Or do I just need to not be profiting off of the vacant unit, technically speaking? There are a few MFH on the market with a vacant unit needing work, so my thought process would be to continue living in my current apartment while updating the vacant unit and using for storage until I could legally lease the last unit. I don't intend to actually live in the unit
-If this approach was viable, how long until I could legally rent out the vacant unit?

-The other approach would hinge upon finding a good SFH deal first and using a conventional loan. I assume then there is no way to make the FHA loan work after buying a SFH with conventional, correct? Disregard my current lease for this scenario.

Thanks in advance for any guidance.