Seeing the long thread in the USMA sub-forum on buying boots got me wondering if there is the same process for ROTC cadets. Do they buy boots before reporting at their school in the fall? And if so, are they basically the same choices as for USMA?
For contracted cadets, they typically issue boots. All bets are off for non-contracted (walk-ons). As others have recommended, having comfortable boots is critical. Should you choose to wait to see what is issued (should happen within about 2 weeks of startup), have plenty of moleskin available. If the issued boots are acceptable, go with it. Of course, if they are not, he is behind on buying and breaking in his own replacements.
I recommend going to your local shop and try some on - everyone has different feet (wider, narrower, tall arches, etc.) and sizes aren't necessarily consistent with what you wear for athletic shoes in all brands. If the standard issue from the unit doesn't work, mail order them that day.
My daughter wears Nike boots. They aren't known for wearing particularly well, but she hasn't had any problems to date (2 years). She also wears Nike athletic shoes (because of the shape of her foot). She seems to feel the folks at Nike build their boots similarly to their athletic shoes.
Depending on where your son goes to school, there are also summer/winter options. It can get even more complicated, but the point here is that you will want to educate yourselves on what is out there and available, just in case what is available to you doesn't meet the cadet's needs.