Even caves need a good cleaning
Science in the News
The first cave that was found not made was in 1975.
Many caves have been made but not found. When the first caves were found everyone thought of a new way for gold. The only way they couldn't would be if it was personal property. So the government put governmental protection on caves that were found in 1990. The federal government would get a portion of the materials that they found like gold, diamonds, iron, steel, and etc.... So then they would all be happy. Recently the government found some dirty caves so they asked volunteers to help clean them up. The government said that they would start in 2016 and be done in 2021.
I believe that the government wanted everyone in the U.S. to help clean caves. They thought that they could try and have government officials clean them but they wouldn't unless they got paid. So the government asked for volunteers to help out with the clean up on caves. This is my main source. http://www.latimes.com/nation/la-na-lint-camp-20150302-story.html#page=1
A cave the size of a small apartment would take about 6 months and maybe a year to clean cut out and remodel the whole cave.
If you wanted a man cave
The average apartment cave would cost around $100,000