When I've entered into partnerships, I've done it with folks who I knew from past business. There wasn't just some informal "Hey we're partners", but clearly defined plans for equity, vesting, performance expectations, roles & responsibilities, etc. I've never been involved in any kind of investment capacity (other than time), and they've all been in the tech sector.
I don't know what the business is, but I hear so many stories of failed businesses in the food and/or drink industry, due to sketchy partners.