Question about Immigration.

Retiring in China is a fine idea, but now it is hard to get residency. A visa is needed and you may need to renew it every year.
Or business would be one way to get the visa F, or marrying a Chinese national so that you are eligible to take a one year L (tourist) visa for foreign spouses and renew every year, or you could get a nice, easy foreign teacher job at a university, in this case, you can take a work visa based on working contract.