Sarah trained worked as a secretary after she left school. She worked as a chalet girl for a couple of winters in Verbier for one of Paddy McNally's companies. She was living in a flat with two (I think) roommates and working for a PR company when she started dating Andrew.

I agree that Fergie was never really out on her own. I think her mother paid for Sarah's flat, or at least a good chunk of her expenses. Sarah was out for a good time and she needed money for that. She has never had the foresight to save for a rainy day or, in her case, several monsoon decades.

I can't see either of Fergie's sons-in-law agreeing to financially support her. Although Jack is wealthy, I don't think it's the kind of wealth that would extend to supporting two households. Edo is definitely the wealthier of the two sosn-in-law, but he's worked hard to get Beatrice away from her mother's entanglements and I can't see him agreeing to have Fergie live with them. I think he might agree to giving Fergie a strictly-controlled small monthly allowance, but that's it.