What you say is correct. What you cannot do is go to a gun store with a buddy that is 21, have him buy for you, and the buy it from your buddy. That would be a straw purchase, which is illegal.
You also will not be able to buy via Internet (Gunbroker.com, AuctionArms.com), as sellers will deliver the hand gun to an FFL Dealer. The dealer will only transfer to somebody over 21.
Bulletin boards at shooting and hunting clubs are a good source of firearms for sale in the local community.