A "single man in possession of a good fortune" has just moved into the neighborhood. What seems to be the chief effect, or consequence, of this fact?

This phrase signals an opportunity for unmarried girls of the surroundings and for their mothers to impress that single man and arrange a marriage of their girls with than man.

Explanation:

This phrase is the first line Jane Austen's novel "Pride and Prejudice" (1813). The full sentence is "It is a truth universally acknowledged, that a single man in possession of a good fortune must be in want of a wife". This theme echoes throughout the novel i. e. the protagonist is in want of an able wife, and the single girls and their mothers of his neighborhood are trying their best to impress that man (Fitzwilliam Darcy).

Replacing "must be in want of a wife" with "has just moved into the neighborhood" makes it more centered toward unmarried girls and their mothers of the neighborhood and less toward man.