Most shuls/halls will not allow homemade food to be brought in because of kashrus. If you’re making a kiddush in your home, and serving food that others brought, that’s a different thing.
I made a kiddush for my daughter in my home. It was significantly cheaper than doing it in shul (over $500 less) and honestly, the caterer my shul uses doesn’t make such great food. Did some people bring over things? Yes. I also know that they’ve hosted many people in the community for Shabbos meals, so people trust them.