Hello Bigger Pockets Community!

I've come across a situation that I'd love some insights and feedback on.

I have a family member who is looking to start his real estate portfolio. He has some money put aside but with his current income, he couldn't qualify for much. However, with him being a first-time home buyer and with rate as low as they are in our market, there are options.

That being said, I'm currently kicking around the idea of co-signing with him. If I did that, I could bring additional cash to the table as well as significantly increase the property he could live in. On his own, he could qualify for a place with 2-3 bedrooms but with me as his cosigner we could qualify for a 5-6 bedroom place -- obviously much more ideal for a cash flow.

Here's my question -- how do you split this up so it make sense for both of us? 

For my family member it's his primary residence. He's simply house hacking. I'd do it too if if I were in his situation. But with him living in one of the rooms, that could cut the income on the property by $400 - $500 / month.

For me it's an investment right out of the gate. My focus is cash flow and appreciation. 

Any insights on what's worked for others in the past or possible solutions of splitting cash flow would be helpful.