It's risky. Suppose he will be doing something stupid or illegal while working under your company name. Then your company will be held responsible. Could take you into legal troubles you'd prefer to stay far away from. I'd never do it.
Why not sell him the LLC? Then it's his. Or let him start his own LLC if he prefers that above being a free-lancer.
I've got an LLC in Texas that I currently am not active with. A friend has asked if he can work under my company name doing some freelancing and I'm wondering if there is anything against this or if it will cost me anything down the road. Any help much appreciated.