its a Investment, dont skimp.
I would avoid the recurve type.
the longer the Draw the more energy=knock down and range.
the reverse limbs are pricy but IMO worth it.
Check out the scopids
http://scorpyd.com/store100.html
you may be able to find a nice one used.
many states limit fps so be sure you know what you need.
Don't be fooled into thinking a crossbow is like a gun nor bow.
its different from both.
IMO get the kid one of the Upgradable Bow packages if cash is of issue. I forget the name but Bass pro was pushing them, when the kids reach increases you can bring it back in and get a longer limb. it costs but not as much as a new bow.
crossbows have there place but leave many cold. mostly misconceptions.
my 70 lb draw bow will travel nearly 2-3 times the distance my 150 crossbow will.
with more knock down to boot.
now if your in a area they regularly sneak up on you at a close range, crossbows are nice. not to much movement,just rise it and shoot. or if you cant draw back at least 50lbs and know your range another plus for a crossbow.though regardless of what ever you need to always be able to figure your range. just more consistent with the Crossbow.