The papers were discovered by a Nuremberg man among the possessions of his late father.
Hitler spent nine months in prison after an abortive coup attempt known as the Munich beer hall putsch.
Among the documents is a letter from Hitler to a Mercedes dealer asking for a discount on a 40-horsepower 11/40 model.
The future Nazi leader, who brought Germany to defeat and ruin in World War II, explains that his book, Mein Kampf, is not yet finished and he is unsure how much money it will make.
“I am forced to obtain an advance or loan from somewhere. So a few thousand marks makes a big difference,” he writes.
The auction house, Werner Behringer, says the bulk of the documents are official prison cards listing visitors, including more than 30 people who celebrated his birthday on 20 April.