After Jane Walker's death [the maternal grandmother of our Jane Austen], her daughter Cassandra (by this time married to George Austen) [mother of our Jane Austen] purchased £3350 in South Sea Securities, which we may assume represents Cassandra's [our Jane Austen's mother] share of her mother's estate.
I have tried to simplify the complexity by adding information in brackets  due to so many of the family having the same name.
What is interesting is to learn that Jane's mother did have some income/property. I am beginning to think that they were not all that desperately poor. Another interesting fact to discover is what exactly are "South Sea Securities". If anyone can shed more light on this subject, please do.
Linda the Librarian
Pic: Mrs Austen (Julie Walters) and Mr Austen (James Cromwell) in Becoming Jane (2007)