I can't believe the number of people suggesting just a front brake in ... first and foremost is safety ... if he goes that option, has to slam it on unexpectedly one day without the time to think and ends up flying over the handlebars or the wheel tucks in underneath himself and he ends up hospitalized with serious injury .... just make sure you leave your comments here so you be traced via your IP address and you can be sued for his medical care (and anybody else he may hit) thereafter for the poor advice you've given ... personally I think the comments are totally irresponsible as it's dangerous to even suggest it.
I'm sure this will create a few flustered responses .... I'm off on a 3 day cycle tour early in the morning so won't be checking in here in case anybody accuses me of throwing a grenade in the room and then disappearing as that's genuinely not the case bit I honestly think people need to think through the advice they're giving and the repercussions it may lead to.
I think 2 brakes or don't ride and just to save a bit of money to risk your own and other people's health is totally irresponsible.