Get ones you can release into your yard. (Make sure they are releasable, most aren't.)
This way, you can hatch an ootheca, feed off all the babies you don't want or release them. Raise 50ish or so to a good size then keep afew for breeding.
They will eat tons of crickets, but by reducing the size your raising itll be easier. I've also had a buddy of mine who raised Mantids for his Bearded Dragon, he would sell 75% of the hatch to gardeners as non-toxic pesticide.