He needs to learn about colloidal silver or sodium thiosulfate of he wants seeds. He’s going to end up with a bunch of non-feminised seed, half of which will be male.
I would be torqued off if one of my neighbors insisted on maintaining a male plant anywhere near my outdoor grow.
I heard pollen can travel up to 25 miles on a good wind.
A tent could help as long as you yourself don’t get any on you but if its in the air just opening the tent could let it in…
I would say it would help a lot, especially if you have a filter. I have a buddy that did the same thing. He lives about 2 miles as the crow flies, but I talked him into destroying it before mine were very big.
Be a good neighbor and learn using chemical pollination with him I suggest. Win Win and a good growing relationship and friendship could develop. Just me. I hate stress so I avoid it all i can. Already had enough.