[capt_noonie]

It sounds like to me if the MIL is going downhill and being admitted to a nursing home (and not senior living complex) that she likely isn't going to improve. If you want to keep the dog yourself, you need to get them to sign a surrender form. If you want to take the dog to visit the MIL that's up to you, but usually with rescues, we are not allowed to bring the dog back to the original owner bc it's confusing for the dog.

As for vet bills, if you get them to sign the dog over to you, then you take care of vet bills, unless you can get the dog into an actual rescue, but even then it's only necessary vetting that's paid for. I always pay for nail trimming, food, clothes, grooming supplies, etc out of pocket. If you want him to be put in rescue, and aren't already a foster for a rescue, you'd have to find one that would take you and this dog. Not sure how that would work.

I did foster a yorkie before I was officially a foster mom with a rescue group, and he was also given up by an elderly woman. I at first intended to keep him, but Uni would torment and bully him, so I interviewed families myself until I found a match. I assumed all vetting while I had him.

Whatever you decide, I agree with the others, get it in writing.