These government surveys are usually large and authoritative.
In Google, click "Advanced Search."
Scroll to the bottom to find "Topic-Specific Searches."
Click U.S. Government.
Type "Money Statistics" into the search bar.
http://www.census.gov/hhes/www/income.html gives stats from the U.S. Census
http://www.statistics.gov.uk - Free access to the UK's Office of National Statistics. Select the theme "Social and Welfare."
Most surveys get into the news. Find an article reporting the study to trace down the source.
Google News http://news.google.com/ is good to help find the most recent studies. (The search orders pages starting with the most recent articles.)
Google News Archives http://news.google.com/archivesearch allows you to search historical archives. Searching "money survey" yielded some great articles. Unfortunately, some of the articles give only a couple of paragraphs of teaser before requiring a subscription.
Gallup Polls http://www.galluppoll.com
These respected pollsters provide brief summaries (or descriptions) of their polls, but require a $95 annual membership to access the poll and their analysis.
Polls on Youth and Money
Junior Achievement www.ja.org does many polls of students concerning personal money management, careers, entrepreneurship, etc.