Help me take care of my rescue cats!

Hey guys!

So long story short, my grandparents left me the countryside house with 17 rescue cats. Now that wouldn't normally be a problem, but now, there are 6 female cats, and are looking for a mate, and I'd like to sterilize all of them. The vets are expensive, and so is the food, so right now, I'm giving around half of my salary (I work as a waitress, while also studying Psychology) on their food, and every kind of donation would mean a lot to me since I'm all alone here (my grandparents were the last relatives I had), the bills are pilling up, and I'd like to take care of this before one of them gets pregnant again. Thanks in advance!