Sort of sounds like it could be a hairball. But....constipation and vomiting do sometimes mean a blockage of some kind. Have you tried the OTC hairball remedies? They make a paste that you put on the kitty's foot and she licks it off. Hartz makes it and you can find it at your local grocery store.

Explain your financial circumstances to the vet. Most likely they'll accept some sort of payment plan or even reduce the fees for you. I've done it - and they readily offered me a discount. They're jut glad that you're taking care of your pet.

Good luck....I hope your kitty feels better soon!