Is it illegal to accept money from clients?

Good day, I'm curious about a matter related to financial practices. Specifically, I'm wondering about the legality of accepting money from clients in the context of cryptocurrency and finance. Is it generally considered illegal to do so, or does it depend on specific circumstances and regulations? Are there any key factors or guidelines that one should be aware of when it comes to accepting funds from clients in this field? I'd appreciate any clarification you can provide on this matter. Thank you.