Background

Dear Teacher,

There is a paragraph:

It's hard to ramain anonymous these days. Information is available on just about anyone: credit files on microfiche, service records, lawsuits, marriages, divorces, wills, births, deaths, licenses, permits, vehicles registered. If you want to remain invisible, pay cash for everything and if you err, don't get caught. Most of our personal data is a matter of public record. All you have to know is how to look it up. What your state and city government don't have on file, your next-door neighbor will usually share without so much as a dollar changing hands.

Question: This paragraph is about America life. Please explain the background of this paragraph. How could a person reamain invisible if he pay money?

Question: Pleae explain the meaning of the last sentence: What your state and city government don't have on file, your next-door neighbor will usually share without so much as a dollar changing hands.

What's the function of "What" in the sentence?

Thanks.