Looking after a grand child must mean there is another adult, maybe two around who could give you a hand.
I bought mould killer from B&Q worked like a charm, and a little block gizmo from Sainsburys (but available in DIY sheds too) that stops mould appearing.
If there is wood under the carpet then the floors may sand nicely if the carpets have had it.
Cobwebs ? The easiest thing of all to get rid of.
If it is his attitude that he really doesn't care because he isn't there much, then you do have to either tackle that or tackle the jobs yourself.
That debt must rankle a fair bit but, if he came to you with the debt and you knew that, then nothing much to reproach him for.
Make a start yourself and see how far you get with the little things, then enlist help and maybe he will join you, if not there will still have been an improvement, however small.
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