So far the main thing I'm noticing in this book, financially, is the characterization of Mrs. Norris. She thinks she's being sensibly frugal, but she's actually cheap. Happy to volunteer other people's money for Fanny's care and future, but shocked when anyone asks her to contribute. Coming up to Mansfield not because she wants company, but so she doesn't have to order a dinner that day. Totally supportive of the planned expenses for the play, as long as she's not expected to help out.
There was a passage early on that I'm having trouble finding again, to the effect that if she had had children, she might have got used to spending all their income and never saved a penny, but having instead gotten in the habit of putting some by, she never liked to spend it, even once she was living alone and comfortable. I think this happens to a lot of FIREees, early on in RE - it's hard to change from a savings mindset to a spending mindset. We have to work to overcome the aversion to taking money out of savings, and seeing the balances go down.