A new friend recognizes and needs your expertise and invites you to be a project shareholder. Should you join?
If you particularly like this new friend or the project, then give it a try without extra expectations. You will always gain experience.
The safe approach is that you can exchange your expertise for consulting fees.
In this way, you don’t have to use your own funds to take risks, won’t regret having no profits at the end of the project, and don’t have to worry about the time-consuming communication among shareholders.