I'm age 21-22 with minor diffuse thinning. Would I be a good candidate for hair transplant?

If you have diffuse thinning you probably would not be a good candidate for surgery.  You should see a doctor for the right diagnosis.

would be a good place to start but in general it sounds like at this point you may not be the ideal candidate. 

Impossible to say without an in-person evaluation--or at the very least, a preliminary consultation via Skype/photos/video. There are a good reasons most hair transplant surgeons take a conservative approach to hair loss in younger men, but it is conceivable you might be an exception to the rule. I think it is important for you to see at least two experienced, full-time hair transplant surgeons to get some guidance. In the meantime, if you haven't already discovered camouflage products like Toppik and Hair Illusion, you might want to check out the YouTube videos and give them a try. Thanks for your question--hope this was helpful.Dr. Ballon

We generally do not recommend hair transplants in 22 year old males because the final hair loss pattern is not evident so that long term planning can't be done properly. Starting at this age may commit you to a lifetime of hair transplants if your pattern is eventually advanced.  Don't rush