"A single man of a large fortune; four or five thousand a year"

With a very little literary detective work it is possible to find out how much this means in modern money. The events in Pride and Prejudice are widely considered to begin in September 1811 (see here for more on the book's chronology).

Using the brilliant and rather addictive historical price converter found here (on the right hand side of the page, scroll down towards the bottom) this income equates to an annual income of £260,000- £320,000 ($407,706- $501,792 approx.). Not bad indeed.