And for me, the biggest lesson to takeaway is if someone is proposing an unusual arrangement, there is usually a reason why and to be wary.

A few months in now, my downstair neighbor mentioned that the previous owner made an arrangement with them and said they can do a sound test inside the unit.

Depending on how you will arrange the agreement.

That arrangement sounds far-fetched!

But because it sounds like the whole arrangement was off the books with an unlicensed guy it gets kinda fuzzy.

@Janille JacksonHUD guidelines allow borrowers to do their own work on a 203k (called a self-help arrangement). 

While not the reason why I do this, I’m sure it at least gives some pause for thought before some folks break up and bail on a lease arrangement.  

He DID have a verifiable job workign with pre-schoolers (so you know THEY screened more closely than I'm allowed) which in combination with the other resident income easily met that threshold.    

You'd still have to get your FHA loan as an individual and keep this side arrangement with partners off the mortgage.

The point is, without the estoppel letters to prove what the current arrangement is, the tenants can say whatever they want once you own the property and the seller won't be around to help clear it up because they're not even helping you now while they still own it.