Can I fund fam member's FHA 4plex purchase & share cash flow?

[Caleb Christopher]

Poke holes in this:

My 19yr old cousin wants to invest in real estate as do I. I already have a single family rental I am thinking of getting a HELOC on.

I want to co-fund (willing to co-sign) the purchase of a 4plex for cash flow that he'll live in as a primary residence.

Here's the strategy: Leveraging him for FHA primary residence first house lowers the cost of entry and expands our market to properties up to ~$200K. (We're not after just any property, it needs to do the right pure cash flow with conservative estimates).

I don't want the performance of the investment to rely on him (has to work whether he decides to do maintenance or not).

I need commentary on which kinds of contracts, promissory notes, or other documents can be used to structure the investment cash flow 75/25% me/him.

I don't need mortgage or title transferred to me; just some structure that directs the cash flow (probably best rent was managed by me).

I would also want some agreement he won't leverage the property for any other purpose.

I understand the interpersonal risks, but not all the legal implications, and I know contracts are only paper. I believe my monetary risk to be just my investment (unless I co-sign). So if things go south, I'm ok to cut my losses. I'm only going to invest what wouldn't kill me to lose.

Does this strategy have good bones?