Quixote is contemptuous of property ownership, hates slavery, and is deeply enamored of marriage.
Quixote tells Sancho Panza and the goat herders a tale about a supposed Golden Age in which there was no property and in which men lived in harmony with each other. This is an expression of a belief that property causes discord between human beings, making them greedy and giving them an excuse to be at each other's throats.
Somewhat less eccentric is Quixote's detestation of slavery, which was very much a minority opinion in Cervantes's day. In the novel, Don Quixote and Sancho Panza head off to equatorial Africa, where they liberate a population from a giant. After this feat is accomplished, Sancho Panza wants to sell these people into slavery, but Quixote is opposed to this and remains resolutely anti-slavery.
Quixote is deeply enamored of the institution of marriage. But given his romantic nature, it's not surprising that he thinks that marriages should be based on love and not on economic interest. For him, unlike so many of his contemporaries, marriage is meant to bring happiness, to meet his emotional needs, and to give him a sense of security.