Legal Question in Business Law in California

In most circumstances yes. To protect yourself, best to have a written agreement with the party paying it and a disclosure to the person you introduced although neither are required.

Hope this helps and good luck in the new year.

If the payment is correctly labeled as a finder's fee, it is legal. However, persons acting in a self-described role of "finder" often have stepped over the limit and have performed services for which a license is required. In a real-estate deal, for example, merely introducing a buyer and a seller is a permissible finder activity. However, if the "finder" gets involved in advertising for buyers or sellers, or becomes involved in the price, financing, etc. negotiations, very likely he or she will have done what is considered the activity of a broker and will not be entitled to a fee.