From Wikipedia (prior to elected office): advocated for nationalization of major industries, including those in the manufacturing, energy and banking sectors. In 1974, he advocated for a marginal tax rate of 100% on income over one million dollars, saying that "Nobody should earn more than a million dollars"

https://en.wikipedia.org/wiki/Political_positions_of_Bernie_...

I doubt Sanders still advocates for most of these positions, and he is of course a millionaire now.