Multilevel marketing/pyramid scheme: Red flag in relationship?

It depends on several things.

Some might just be naive and got sucked into it. In that case, they’re not necessarily problematic, but I would question their decision-making skills.

The ones who are aggressively trying to recruit friends and family members, using manipulative tactics, I would be more concerned about. If they’re willing to basically do this to people they’re close to, I wouldn’t trust them.

Ultimately, it’s hard to say an MLM is a scam. Some people do make money, but the tactics are questionable ethically. The people at the bottom lose money and, clearly, the people at the top don’t care about that. Also, the time spent trying to recruit people is unpaid. You’re better off working at a normal job that guarantees your pay by the hour.