[Reposted because original was too long.]
Some years ago, a high school friend insisted on coming to visit. We lived 800 miles apart. At the time, car and money problems made this a bad idea and I told her so. But she was pushy. She stayed for nearly a week, and once she left, I resolved to cut all ties. It took her a couple of years to get the message.
I spent a long time resenting her for this, until it finally occurred to me that I had done the same thing in previous years to friends who seemed to have lost my contact information after I went home. It was only after I did some hard reflection that I realized that my friend's visit to me was nothing short of karma.
My advice: If someone invites you, completely unprompted by you, say yes, but only if you can afford to treat them to meals, gift cards, etc. If they say ten days, make it four. They are not an Airbnb and you are not a charity case. Sometimes the best friendships thrive at a distance.