In Jane Austen and the English Landscape, Mavis Batey considers that it was important that Darcy’s home reflected his true nature. She suggests that Jane Austen thought a great deal about Pemberley and had a clear plan of the house in her mind. Perhaps, Batey notes, Cassandra may even have drawn her sister a sketch of the imagined landscape.
She suggests that Pemberley was modelled on Chatsworth, the home of the Duke of Devonshire because she placed Pemberley in the vicinity of Bakewell although, as Batey points out ‘Darcy was no Duke of Devonshire and Chatsworth could not be kept up on even £10,000 a year’. - Country Houses in Jane Austen's Novels
This article in the Victorian Web Nineteenth Century Household Staff discusses how many servants it would take to run a townhouse or a country estate, and the minimum costs involved in 1857. Also read: The Assistance of Servants: Jane Austen Centre Magazine