I hope this message finds you well. I am a licensed attorney with over a decade of experience handling matters of a similar nature for clients. It is a pleasure to assist you today.
The answer to all three questions is, yes. That said, let's discuss for a moment why the answer is yes and what you can do to assure that there is credibility behind the certificate.
You can provide a certificate or completion/passing for successful completion of your class. It is always best that you either have this class certified by a respected licensing body in your field. That is not absolutely necessary, but it certainly helps. I would also urge you to send the curriculum out before the class, make sure the curriculum is the same, is standardized and meets applicable industry standards as well. You will want the author of the curriculum to have credentials as well.
I think you do need to have proper qualifications to teach a class and present certificates. This can be engineering degrees, state or federal licenses, association recognition, etc. You need something that is universally recognized as making you an expert in what you are teaching...otherwise, you will be discredited and the certificate you issue will not have the credibility necessary to make it worth the effort and expense of the certificates. Is there a law that mandates, these things...no. However, from a business and credibility sense, you need these things.
You can charge for the certification. Again, you need to have the weight of credibility behind the cert or people will not be interested. This can again be recognition within the industry by licensing bodies or trade associations...but there needs to be something there. Once that is in place, you have credibility and legitimacy and can charge therefore. This is more business-centric than legal.
Let me know if you have any other questions...I want you to be as comfortable as possible moving forward.
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Best wishes going forward!