Do I need to be a millionaire rapper to judge someone's music, or to know about music production? Music production is tedious, but a lot of producers sit around acting like their anal retentiveness does anything special. There's certain ways of getting sound to sound good with each other. When you're sampling other things, it's more of a matter of getting already produced stuff to sound good with other stuff, which is possibly less tedious, because it's already recorded and engineered. Getting the samples to line up to beat is just a matter of changing the rate and bpm of the tune, and just messing with it until it does. I'd imagine that rappers listen to lots of music and then fit parts of other songs together to make their song. I mean, I'm not joking that finding obscure music to sample is a part of all hip hop. Look at any hip hop song's sample list and you'll see a bunch of obscure sample credits. They're just songs the producer listens to and likes and decides to use in their new tune.