Planes don't have modes attached to them. Radios are set up as Mode 1, 2, or whatever. If he buys a bind and fly plane and has his radio set up as Mode 1, it will work with Mode 1 control.
Since nearly every radio on the market is designed to be sold all over the world, and since most European pilots fly mode 1 (explaining why mode 1 dominates F3A btw), nearly any radio you consider buying can be converted with just a little bit of screwdriver work. This is really a non-issue.