The old man went to the children's social security and moved to Hangzhou.

Conditions for the elderly to take refuge and settle down:

Men over 60 years of age, women over 55 years of age or men over 55 years of age and women over 50 years of age in Hangzhou, both husband and wife are in other places, and there are no children around them. All or most of the children are in the urban area of Hangzhou, and the children have legally fixed residence in Hangzhou (including commercial housing, affordable housing, low-rent housing, self-run housing by units with lease certificates, and public houses directly managed by housing management departments). You can apply for asylum for the elderly at the police station where your child is registered.

If you have your own house in Hangzhou, you should be able to do it in principle.

As for social security, because the payment in the two places is different, the pension and medical reimbursement after transferring to Hangzhou must be somewhat different from the local payment in Hangzhou.

Further reading: How to buy insurance, which is good, and teach you how to avoid these "pits" of insurance.