if he gets to the point where he decides he needs one, he can buy a new frame for $150.
there's nothing wrong with spending $350 on a bike he can have fun with and not sweat locking up in the meantime.
to be completely honest, a low end bike with fun colors strikes me as a nicer idea than a low end bike wih no options and an endorsement from a web forum full of people who don't know much about bicycles in the first place.
a bike that won't see more than 10-15 miles a week doesn't need to be anything special...