Is the $2000 budget with optic or without?
If it’s without, I’d encourage him to spend an extra $300 and get a KAC SR-15.
If with, there are PLENTY of quality factory guns with warranties he could get within his budget and still get an optic. If this was his nth AR, I’d totally understand doing a custom build. But if you guys only see each other once or twice a year, the last thing you want is for something to not work with the rest of the system and it not run correctly and you’re not around to troubleshoot/fix. If he gets a rifle from a reputable, quality company, and something goes wrong, at least he has a warranty and can send it back.
Plus, unless you have tools to properly stake castle nuts, pin gas blocks, and headspace bolts, it’s not going to be as bullet proof as something from LMT, KAC, SOLGW, BCM, DD, Colt, etc.