20+ years ago, my adult child asked how I'd feel if they and their partner moved into my house (large three bedrooms, I was on my own). We had an adult conversation about it. Things like privacy, me having male friend stay over and, of course money.
We agreed that I would pay the bills, utility and mortgage, they would buy and shop for the food. They would be responsible for managing the upkeep of the house, we would each pay a share of the upkeep.
We would each have our own living spaces during the day, but no restrictions on sitting in each other's space. And both our bedrooms were out of bounds for the other, except in emergency.
For all these 20+ years it's all worked pretty well, by and large.
Your children are adults, having an adult conversation with them seems to me is what's needed. Telling them you are struggling to meet the family's financial commitments and asking for their help in meeting what are joint responsibility seems a good starting point.
not a shouting match when you are under, for example, financial pre ssure, but a reasonable and adult conversation.