Vet & Supply Costs For Kittens

A stray cat had this litter of kittens & abandoned them. Another small female stepped in & started nursing. She is very underweight & needs to be seen by a vet. There are 4 kittens, 2 male & 2 female. I brought them in on Sept 24 to foster & try to find them safe homes, as it is dangerous for them in my neighborhood. The kittens are approximately 6-8 weeks old. There is a male stray still outdoors & I would like to get them all spayed & neutered. I already have 4 resident cats so this is putting a strain on my budget, but I couldn't just leave them outdoors. Any help is absolutely appreciated! I want to find these sweet souls loving homes & know that they are healthy when I do so.