Hey Mike,
I'm doing exactly this, because I live and work in the UAE, and because I'm paid by the UAE government (no W-2), I don't pay taxes in the USA, so it looks like I don't get paid period. Aren't banks awesome? So I'll use my current situation as the example.
I bought a house for 70k using owner financing, and I intend to flip this house. They were kind enough to let me put zero money down and do an interest only loan, meaning I pay nothing up front and I pay the interest, taxes, insurance, and utilities every month from the time I assume the property until I sell the property. This makes the holding costs lower.
I know the rehab cost will be about 30k. I also know from the comps that the ARV is around 150k. Like you, I brought in my close friends and family, those who have shown interest in real estate, and would like help getting a foot in the game. Since the deal is so nice, it was relatively easy to convince them to contribute for a return. I also told them that everything will be documented from the very beginning all the way to when the house is sold. Everything. This is my gift to them for trusting in me to invest their hard earned money.
For example, and this is just to illustrate the figures, let's say the profits are expected to be 30k. Let's also say I raised all 30k from friends and family, meaning I'm putting in zero dollars. One member, mom, contributed $3,000 to the rehab, which equals 10% of the total rehab cost, so she will receive 10% of the profits.
But wait, your time for facilitating this deal is worth something too. After all, a professional must be paid for his services. In my deal, for putting it all together, my fee is 25% of the profits before any other profits are paid. 25% of $30,000 profits equals $7,500. That money goes to me. The remaining $22,500 gets paid back to the investors. So mom, who contributed $3000 (10%) gets back her $3,000 plus 10% of the profits ($22,500), which is $2,250. That equals $5,250, which is a 75% return on investment (2250/3000 = 75%).
And you, just for facilitating the deal, make $7500.
I would recommend speaking with a real estate attorney, which you can find on BP like @Jynell Berkshire, to help you draft a contract that covers everything you need. I'm sure others will be willing to help you too.
I know this isn't your exact scenario, but hope it helps get you closer to your goals. Good luck.
-Michael Volek