Family and friends as investors

Hi BP community. I just bought a house (first purchase) from an owner and looking for ideas on how I can flip this house with the support of friends and family. I'm not sure if this info will help but, I purchased the home for 20k and looking at around 20-30k to repair. I noticed that similar homes sold for 100-140k after repairs. I guess my question is, does anyone have an idea of how I can have friends supply me with a monthly budget for repairs and in return, offer them a percentage once,  or if, the house sells? I know first things first, is to get my numbers in order but how about drawing up contracts or a business plan that would explain how I would go about the flipping to ease any concerns? Does anyone have any suggestions on how to start?