Have them send you a screen shot of the tribe ownership settings. Make sure they are set appropriately. Personally owned I believe do not merge? But not sure on that.
Straight up if his personal name ingame is on the walls and structures its a scam if it just says metal wall 15k durabiltiy and no personal owner u can merge and itll be urs
You have to invite him to tribe, HE has to merge, and you'll own it, doesn't matter if his governance is personal or not, I've been through that and I was still able to demolish shit
Make sure he's the owner of the tribe your taking in, when the owner presses accept invite everything is brought over (If the setting is correct) If he's just an admin nothing will be taken over