I wonder if, in this type of situation, doing something for someone associated with the person might not alleviate some of the burden of an unpaid debt.
After all, Harry transferred his debt to Charity, and Summer was able to use that to help get Molly back in PG.
True, but that required an action on Harry's part. Harry specifically transferred the debt via oral agreement. If he's dead, can that debt ever be repaid? Perhaps if Harry died and became a true ghost (discounting Ghost Story), Summer may have rendered service to him, clearing his debt?
It's odd, because assets usually default to the next of kin, but not all debt is passed on—outstanding accounts are settled with the deceased assets, if they have any, and the remainder is divided among the estate. If someone dies upside on their mortgage, for instance, and doesn't have enough assets to cover the debt, the estate is not responsible for paying the rest (though the bank gets the house).
Maybe Harry should consider supernatural life insurance now that he has Maggie to worry about.
By the way, I just realized that Harry's apartment burning down was foreshadowed since Book Five, when he wrote down (and told us) about his fairy cleaning squad. It didn't matter anymore, because his house had already been arson-ed when he wrote it (sad face emoticon). I love in-universe justifications for things like that. Maybe his new pad can contract a fresh Fresh Squadron, but pay them with pizza. Or, I dunno, celery.
