Hey Jireh!
When you enter the world of digital products, you start dealing with copyright.
Please note, do not take my words here as legal advice.
Whether we're talking about selling beats, a book, a picture, a poem, lyrics, or anything under the umbrella term of "intellectual property", a much different way of thinking starts to happen compared to a normal 9-5 job.
When we are employees at a typical job, we often go to work, collect our pay check and go home. We don't think about ownership, or "the right to use".
Selling beats would fall under the umbrella of copyright, where others cannot use your work without the proper license.
Can people use your beats without your consent? Yes, you can't really stop them.. and if the person using your work is very small, and collecting little money off of your work, taking legal action would bring little reward for the time, money, and effort you'd have to put in to stop them, and recoup a small amount of money.
If that person is large, and using your work, this is where hiring a music lawyer would come into play, and you'd still have to figure if it's worth your time in regards to how successful they have been off of your music, royalties they've been paid, etc.
There are ways to prevent artists from using your music to an extent..
You can use beat tags.. but the artist can still cut that part out of the beat..
Nowadays many streaming platforms have Content ID systems in place which can trigger a message to either not let them upload the music at all, or those royalties would be passed onto you.
What they say is as soon as you create the beat, it is your copyright. No need to submit it to be officially copyrighted, as that is expensive and time-consuming. You also have the music project to backup proof that you are the owner of the work.
Additionally, if an artist is ripping your music from a streaming site, it's often low-quality audio they are getting. When they purchase a license, you'd often be sending them the high-quality .WAV so they can get the best quality product to their customers, as well.
In short, if an artist is serious about their music career, they will want to purchase a license to the right to use so that they can perform, record, and sell their work over top of your work.
What are your plans with this knowledge?