To anything like a permanence of abode, or limitation of society, Henry Crawford had, unluckily, a great dislike: he could not accommodate his sister in an article of such importance; but he escorted her,....

I too am wondering about this. It makes it even more of a wonder when Henry stays for an extended period with Mrs. Grant and Mary due to his dealings with the Bertram family.
What would it have cost him to allow Mary to reside with him in a large home? Unless there was something else there. Perhaps Henry was a man of dubious character who had many lady friends visit? Or perhaps Mary's character may leave something to be desired?