A buddy at work asked if I could reload some ammo for him and he would pay me for time and materials.
Can I do this legally? Or do I need some kind of FFL license?

What Ridge said.

I reload for my two of my brothers and my father...but would never consider loading for a "friend"...for the same reason RR mentions.

Besides all the liability issues involved your buddy must think your time has no value.
Not just no...hxll no.

I load for a very close friend. He likes guns but isn't much of a range guy. Every now and then he'll get one that doesn't shoot up to standard. I'll do the load development and range time, he pays for components, dies etc. I get the enjoyment of loading and shooting on someone elses nickel, he gets taylored ammo. Many people have asked, all but 1 have I refused.

Receiving a fee for services (time & effort) opens more than one can of worms.

You need an FFL if you are planning to sell your reloads. It's also a good idea to have tons of insurance. Not worth it in my opinion.

I reload for my brother, brother in law and nephew. If the guy seems decent (I've done this about 4 times, they never come back) I will them use my setup to reload there own under my supervision. That seems to be more to answer a "do I want to reload question" than anything else. But because of the liability, to answer your question, no I don't for any one but family

You do need a FFL

If your reloads caused something blow up you would be in so much trouble,
You could kiss every thing you own Good Bye, along with your being able to own guns again.
So Don't reload for a friend.

Ain't any way to keep a friend I feel. Even if you could win a law suit think of what it would cost to have a good lawyer to defend you.
And Never loan any tools guns or any thing else you like having.

Let him buy his own equipment and set down at his bench and run him thru the steps sans powder in a case.

Al