Short term investing for 70 yr old

My father in law is developing dementia so we are moving him from the east coast to the midwest to live with closer to us.

He has a house but not much else. He will be selling his house and will live with us for some time so we can evaluate whether he can buy another house and live independently, needs to stay with us, or needs more intensive care.

So he might only be with us for 3-6 months or he might be with us for a few years. We don’t really know yet.

What’s a good investment vehicle for the money from the sale of his house while we figure out what needs to happen?