Take Him to a Bow Shop and have him try out several different Crossbows....there are so many different ones and prices vary from cheap to very expensive and You can get one with either a pull strap to draw back the string or even 1 with a hand crank.Then there's a variety of different scopes to choose from and many different styles.
I've been looking at the Excalibur Crossbows and like the way they are made and the simple limbs they have on them.There a are many different ways Crossbows are set up,length and weight that You need to check several different Brands out to see which ones fit the best and the weight is distributed the best for shooting.