Loaning money and business deals with family and friends? It's a very, very bad idea. This advice has been around for ages, but you always tend to think that it will work out in your own case. It won't. Ask me how I know ....
If you go in with the mindset that you're simply giving them the money as a gift, it will all be good. Then on the odd chance that you actually receive a few payments, it will be a pleasant surprise.