I am perhaps in the minority here in that I think Greer does have a serious, for-real, life-impacting disability. He can't speak clearly, which is a huge problem. A lot of jobs are just going to be out for him because he can't have a phone conversation.
For example, he would struggle as a lawyer. Sure he could Tard through law school with accommodations, but being able to speak smoothly and understandably is damned hard to work around. If he isn't some type of savant in a rarified solicitor field, it's going to be hard.
Also out are the charisma-heavy jobs. Realtor, broker of any sort, higher end retail, sales. And hospitality. Also all of education gone. Accounting is out. Anything where he has to be face-to-face with a client communicating is not a good choice.
What's interesting about Greer is his determination to do one of the things that would NOT work. Instead of programmer, A/C repairman, forklift operator, he wants actor, litigator, singer.
We are all working with the hand we've been dealt. I have a pretty shocking lack of charisma, and I knew early on that any form of sales would not work out for me. I'm good at paperwork. I do things that require paperwork, not things that require shmoozing. Everyone is making these sorts of calculations.
Greer is like the person so dumb he actually believed "You can do anything." He's Kyle wanting to be the Jewish basketball player.