"still working on prototype, no sales or funding yet" If you want to join as an employee, then they need to pay you a decent salary. Even if a bit lower than m

"still working on prototype, no sales or funding yet" If you want to join as an employee, then they need to pay you a decent salary. Even if a bit lower than market, you could consider if you really like the idea which could totally fail. But do not join as an employee but no salary (it could even be illegal in the United States but I am not sure which country you are in). If they cannot afford to pay you a salary right now, then you must be a co-founder because they are still in prototyping stage. You need to get a significant chunk of equity (I would argue it should be closer to equal share). Remember in either case, this product could go nowhere and you could end up with nothing. But if the risk is worth it to you, then make sure you are protecting yourself properly.