Neighbor starting Rooster Farm

[Ol Grey Mare]

You may be Cock-A-Doodle-Doomed.....starting at about the 3 month mark.

But the 125 birds in a 10x10 coop is crazy ridiculous......wonder how big the fenced in part is?
The stink could be prodigious, way before the crowing starts.

If you have a good relationship with him maybe a little conversation is on order, especially if he hasn't had any experience with chickens.
Meanwhile might want to look into the local laws, just so you know...and can let him know.

X 2
If possible, a good neighborly conversation may go a long way to address some of the concerns you have as he may be able to better explain his plans and clarify things in such a way that it answers the possible issues. Having the facts regarding the legalities will be helpful if this fails.