We have a pretty good idea of how wealthy Hitler was and how he managed his affairs because we have his Will and his tax records.

For comparison reference for figures below the average German worker in 1933 earned 1,200 RM (Reich Marks) per annum,

Hitler publicly declared that he would forgo his salary of 29,200 marks and his annual expense account of 18,000 marks when he became Chancellor in 1933, however in 1934 he reinstated them without notifying the public. You get to do that kind of thing if you're a dictator.

He also amassed wealth through tax evasion, royalties on Mein Kampf and the use of his image. For example he put his face on the stamps then included a royalty charge on them. Another thing you get to do if you're a dictator. When he was Chancellor he no longer needed to evade tax as he just ruled that he was not subject to tax laws. You may be able to detect a pattern here.

His final worth at death is estimated at $5 billion US (current rate) and he's estimated to have owed about $8.7 million US (current rate) to the tax man before he became Chancellor.

http://www.thehistorypress.co.uk/index.php/updates/Hitlers-will/

http://news.bbc.co.uk/1/hi/world/europe/4105683.stm

http://edition.cnn.com/2004/WORLD/europe/12/17/hitler.tax/

http://articles.latimes.com/1987-01-03/news/mn-2155_1_adolf-hitler

http://www.haaretz.com/jewish-world/jewish-world-news/1.600399

For currency conversions, where GBP or Euro or older US $ figures are quoted in articles, I used http://www.xe.com/ and http://www.davemanuel.com/inflation-calculator.php

Edit - tax owed when he became Chancellor was in millions USD, not billions, typo now corrected.