How can a designer become an investor of a product?

[pixelindot]

In a nutshell, i started helping some of my friends in separate with ideas for products they wanted to take forward. But I rapidly saw that becoming founder of several projs at once could make things confusing, so I distanced myself a bit and made myself design investor of the projects. I own a stake in the product, support with vision and design, but let them be founders.

This became a thing: http://designer.vc and by seeing some milage in it I decided to extend it a bit further beyond my circle of friends. My question is, does this have milage? Owning stakes in ideas that are not yet incorporated is usually about trust and friendship and managing those relationships with a written agreement signed by both parts seems a bit dodgy..

What do you guys think?