If you think you might not have a job in the future (or it would take time for your 401K to recover) explain it to him and only hire him once things are back to normal.
You and your financial stability must come first, he'll understand hopefully. Even if you can't afford hiring him this year you'll be able to do it after you financially recover!
Some of you guys on here are confusing lending money to a friend with prepaying an escort or giving him a booking fee. I've always told all my friends to ask money from a relative.