First of all, please don't introduce them with both of them intact. Females are highly territorial when they're intact. The liklihood of you bonding them now is extremely low, but there's a pretty good chance that they'll fight. If you can't afford a spay, can you afford an e-vet trip to stitch up a bite wound?
I would go ahead and start saving for their spays and let them live next to each other. In addition to helping them bond, it will remove their chance of developing ovarian cancer, which they have an 80% chance of developing and is quite aggressive.
We are as gods to the beasts of the fields. We order the time o' their birth and the time o' their death. Between times, we ha' a duty. - Terry Pratchett.
"Men have forgotten this truth", said the fox, "But you must not forget it. You become responsible, forever, for what you have tamed. - Antoine de Saint-Exupéry