Realistically he's not likely going to give up his car since he would be new to commuting. Therefore you can't really discount the cost of upcoming repairs, or insurance. However if he does a simple cost savings calculation on gas and reduced repair costs, it might be enough to convince him ... especially if he's struggling to meet his housing costs.

Btw, you're a great friend if you're willing to let him choose any one of your bikes. Not something that I would do, however then again I'm a bit stingy.