I hear it's most common in Washington D.C.

Nope, brothels are illegal in DC. There used to be loads of street walkers, but not so many as the city has gentrified, cleaned-up, and crime rates in general have gone down.

I was referring to the practice of political lobbying and revolving doors, not literal prostitution.

For example:

https://www.opensecrets.org/revolving/rev_summary.php?id=787...

I think the key word there was "public."

OP means Original Poster, or the person who started the thread/posted the article. Do you mean GP (duncan_bayne)?

Yes. Thanks for the vocab word.