[carries]

If you are really serious about setting up the shelter, you should get in touch with SPCA, PAWS etc and ask for some assistance from them.

The food cost is not the only expense you will incur.
The biggest expense will be the medical bills.

It therefore makes good sense to try and see if you can link up with an established rescue operation that has full time vet services and try to work out something with them.

Please note that the established animal shelters would be able to help advise you on what facilities you need etc etc

Also, from what i have researched, if you are new and small, you might also want to team up with other small rescuers in your area. That way, you will have a larger pool of helpers and you guys might be able to pool resources.

Lastly, if yours is an actual shelter meaning that you are willing to shelter the animals long term, then you could do an exchange program with SPCA or PAWS where you can trade your adoptable strays for their unadoptable strays.