How can you know that the company is a scam?

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I am planning to join an online business but I want to make sure if this business is not a scam. How would you know that if it is a scam or not? Do you have a link that would provide me an answer? I don't want to waste my money that's why I'm asking you. I need your help. Thank you so much! One more thing, is there a government office that regulates and controls any online transaction? Or a law that should be followed for us to see if it's legal or not?