Closed cans are not a must if your friend is just making beats. I mean really, anything at all will do if you trust the imaging you're getting from whatever you're using to monitor. Really one should be auditing one's mixes on a few different setups (headphones, speakers) anyway, just to make sure it'll sound good anywhere.
In a studio, practically, you really only need a closed-back headphone when you're recording so that sound from the headphone does not get into your mics and back into your recording. And for that purpose, even a cheap closed can will do, if it isolates well and doesn't butcher your ability to monitor your recording.
In my experience, there's a lot to music production, especially just sequencing, that's not going to require a critical-listening level of gear. You can lay down a sequence using garbage headphones or speakers, and you can continue working on a track in this way until it's time to grab your reference monitor and really do some work on the sound, in which case one pair of even really good headphones is not going to be ideal.
Renowned gaming cans like the AD700 or the K702 are going to be a bit bass shy, but as long as your friend considers this when making a beat, he can account for it in his mix. With regards to studio use, especially in a budget studio, an awareness of your equipment's characteristics are going to be key, so really if you pick a decent gaming headphone, and just learn exactly what it's going to do to your mix, you'll be doing alright.
And by "you," of course, I am referring to the general "you" that is more likely your beat-making friend. HTH
