How can I buy him bitcoin and let him hold on to it. His computer is really slow so I'm afraid it has a lot of malware.
Is there a way to give him like a code or memory stick....?
I'd personally download the sourcecode of https://www.bitaddress.org on a clean pc, then disconnect said pc from the internet... Run the main html file, generate a bip38 ENCRYPTED paper wallet, print from a directly connected (offline) printer (at least 2 copies), laminate your paper wallets, store them in 2 different (safe) places, then fund the paper wallet's address.
When you're done generating the paper wallets, reboot the pc and printer before connecting either of them back to the network.
The easyer option would be to buy a leder or a trezor... Best $100 (or less) you can spend when you're serious about crypto. I find ledger's chrome plugin wallet very newbie-friendly, while trezor has a (very small) learning curve (imho), but it's still easy to use.