Or a kid pulls it out... or it's stolen...
There's plenty of decent locking shotgun mounts designed for closets.
But if he's got money to burn and wants to jump through the hoops... .38 special revolver and a good lock box.
In that case - Soon to be Maryland resident should get a G17 and a ton of standard capacity mags (Plus a few fun sticks just because). And a gun light. And a handheld light.
AND TRAINING. Training, Training, training.
OP as much as your brother says he wants a 9mm pistol my vote is for a revolver. He has no experience with guns and we all know the revolver goes bang when you pull the trigger with no stovepipes or any of the other things that can happen with a semi-auto pistol. A lot of good things about a 38/357 revolver.
Ok, so I looked at a LOT of guns at the NRA convention trying to figure out what I could recommend to my brother. I discovered something I didn't know before... I really don't like the triggers on striker-fired pistols.
We don't really need to go down the 9mm revolver track again. I might mention the S&W Bodyguard in .38 to him. I looked at those at the convention and I don't know if I would want to shoot it much at the range, but it may be a good choice for what he wants.
A snub nosed .38 is quite possibly one of the worst choices for a novice.
This.
Plus even 5-6 .38 Special out of a revolver still isn't much. My cousin knows of a woman who had to defend herself. S&W Model 10. 6 rounds. 5 hits on the bad guy. https://abcnews.go.com/US/georgia-mom-hiding-kids-shoots-intruder/story?id=18164812
It barely worked out for her. IMO, 5-6 rounds...of anything... just isn't enough. Too many variables.
1911 .45acp in the $1100-2200 range
He's not going to practice. He's not going to carry it. He thinks he needs a gun for the same reason that someone thinks they need a fire extinguisher. Tell him to buy a 4" revolver, .38 or .357, and a box of good quality defensive ammo. Throw it in the nightstand, where it will collect dust until either he needs it in a life or death situation, or a family member can worry about what to do with it when he is gone.