You can, but you must have a license to do it.
Just like a real estate broker is required to have a license to get a commission for selling someone else’s house, you need a license to sell someone else’s securities. And it’s a hassle to get. We have articles about this in our website library.
The alternative is to become part of the company that is issuing the securities. In that case, the company as the “issuer” can get a “for sale by owner” exemption for selling their own securities — as long as they don’t pay commissions (or “transaction-based compensation” related to the amount raised) to any unlicensed brokers (including their own officers, directors and staff or unlicensed third parties), and everyone gets compensated for their role in management other than raising money.