I found teh analysis of incomes by Edward Copeland in the Cambridge Companion to Jane Austen very helpful.

The chapter "Money" is excellent.

There were certianly bands of incmome less than £2000 per year mentioned by Jane Austen.She lived( together with Cassandra and hre mother) on £500 a year after her fahter's death- so she ahsd persoanl experience of living on a reduced income.

Around £500 per year was seen to be the starting point of gentility( Copeland thinks that Jane Austen's expereince makes her aware that 500 p.a. was not really enough for true happiness! but £700-1000 was prefferrable.It enbales the owner of such an income to live comforably and even to purchase a carriage ;-)

£100 per year was the remuneraton of poor clerks in govermnet office and poor curates.It could supply a family only with a young female servant See Miss Bates.