While you can buy a firearm on the Internet, it must be shipped to a regular local licensed dealer, from whom you must pick it up after doing all the paperwork that you would have had to do in order to buy direct from him. In other words, it's no different from going to a dealer, wanting a gun he doesn't have in stock, and having him order it for you
Does the buyer have to pick it up in person? The question would be the same for non-internet sales. I’d never given this much thought before, but the nearest gun dealer to me, and the only one I’ve ever bought guns from, is on the second floor of an old building, no elevator. Absolutely no way anyone in a wheelchair is getting into that store (or even into the building, since IIRC, there are steps even to get inside the first floor). I suppose the dealer could meet someone out in the parking lot to do paperwork, run inside to the NICS check, go back out with the gun, etc. But isn’t there some provision where people can have someone buy it for them? Don’t I recall Sarah Brady getting in a wee bit of embarrassing trouble over something like this, when she was buying a gun as a gift for her son?