Cross trainers are really appropriate to high impact (weight bearing) exercise.
He should go to a "good" specialist sport shop(avoid chains; JJB etc. like the plague) and get some help. They should let him run around in shoes before you buy them too.
The other problem may be he is trying to hard, go fast slowly especially if he is a beginner. I look after our club beginners and every year someone enters the Great North Run etc; trains too hard , gets injured and never runs again. A recent novice entered the London Marathon, turned up at the club last week to start training!!
I am 57 , been running for almost 30 years and whereas I would like to say age is not an issue, it obviously is. I still have the basic speed but notice the recovery is talking longer.
Why run on a treadmill? If you can't get cold, wet and miserable where's the fun?
Join a club and run in company at a appropriate pace, it makes training relatively easier and more fun.