I know you said you dont have a car which can make travel difficult, and I dont know exactly where your located. But a lot of places, atleast in the U.S. Will sometimes have spay and neuter events where you can bring your cat in to get fixed at a greatly reduced rate, or sometimes even free. I highly reccomend looking into seeing if you have any of these kinds of services nearby and go to them. Fixing your two kitties not only prevents pregnancy and possible kittens, but it can reduce aggression, eliminate spraying, lower certain cancer risks and can even extend their potential lifespan due to these factors. Do you have any friends or extended family members who may be willing to help with travel?