I'm not going to let someone come to my party without paying for food
Why do you want your guests paying for food?
I have a budget to draw. I can't let people eat for free.
It's not nice to exclude people from your party just because they can't afford it. You should be a more gracious host and let them in for free.
I just want people to pay for food.
Maybe you should scale down the food offerings to accommodate your budget. Or save up until you can afford to have a party without spending the rent money. Better to throw a potluck party where everybody brings something.