Awesome! Indoors will help a lot to keep them warm and safe from predators and disease. In my region, most rescues say they have a minimum 2 week lead time to accept any new animals, so if you’re able to get in touch now and let them know you’re willing to foster them until they’re ready for spay/neuter, that often helps a lot to secure a spot in their program, and they might even provide you some supplies.
Sounds to me that you might be a great addition to the local foster team, and then you could take in new kittens once the current ones are ready for homes!
Yeah, the low cost spay/neuter clinics around me are booked solid and have been for years. I had to book mine 2 or 3 months out, and it wasn’t even a true “low cost” clinic.
Looking at pricing at regular vet clinics, spay can be $500-700, and there’s extra fees if she happens to be in heat or pregnant when your appointment finally rolls around, and it’s not clear from my brief search whether those prices include anesthesia, pre-op blood work, etc. The low cost clinics range from free to $120 for spay.