I bought a lower receiver to build an AR.

I live in state X.
I have a friend in state Y who is a gun guru and said he would assemble my lower and make it tip-top for me.

Is there any issues with sending, giving, loaning, FTF-ing, the lower to him for him to perform the work and then return to me at a later date.

He is not a gunsmith and neither of us have an FFL.
Any legal issues? Any inputs, comments, suggestions?

Thanks!

We really need to know what 2 states are involved. Some states, Connecticut for example, have baned lowers by manufacturer (such as Colts with AR15 marked on them, funny they are made in Connecticut ) So you wouldn't want to be caught with an illegal lower.