It may seem like an easy go-to but there are some producers out there who give artists a very hard time after a song blows up. Greed is the root cause most of the time. The producer wants to make sure he's not getting scammed and the artist wants to make sure he's not getting scammed. You always need to make sure you know the terms of “Free Beats”. If not you may go to register the song and get a copyright infringement. To avoid this, simply find you a producer that sells leasing or exclusive rights to beats at a decent price. Having beats that you have rights to can help in the future. You can enjoy your royalty profits in peace!