My Mother is a pack rat and she leaves the house whenever I'm low on money. What can I do?

I really dont understand your situation at all from what you wrote. More details might clear it up.

What do you mean "she leaves the house when I'm low on money"? Where does she go? Aren't you the principle caretaker? If she can leave on her own and go stay somewhere else when she wants, then it's time for you to do the same. You need to move to your own place and handle your own finances and let her handle her own. You are due a life too just like she is. Both of you move on.

TS, with all due respect, why haven't you left the house and started a life of her own during these 20 years? You wrote that she leaves the house when you're low on funds. Are you working? If so, why aren't you in charge of your own finances?

Sounds like your Mom is capable to being by herself. Time for you to move on and have a life of your own.