How Much money is enough before applying for visa extension

On a marriage settlement Visa, how much money is required to be had in saving before applying for the first extension on the visa?

We are currently living with my parents, ( no rent paid ) in a large house, my parents own the house outright.
I have in saving for the application £4,000 plus i am waiting for the sale of my home in Australia which will net me good money,

But at the time of application i have £4000,( which i have locked away) what is considered enough as a guide line or ballpoint figure, also i do not have work yet and most likely wont until after our appointment. is this vitally important for consideration???

Some guidance please by posters in the same boat or have went through the same process

Thanks in Advance.

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