Pardon the odd question, I'm just curious, especially in the early modern era (say, early 19th century), how exactly royal families functioned financially. I know in Britain they received parliamentary annuities, and in other countries as well as Britain possessed real estate, and most especially palaces, ect. They had art collections, were the holders of things such as forests because as the sovereign they were the state. Royal Princes in the Ancien Régime derived income from appanages, but how exactly did a royal make money? There are plenty of royals who were impoverished, often running up titantic debts because they couldn't afford to live the way they were supposed to be maintained. They couldn't really work like a typical person, and while they may serve in the army or something like that, the income wasn't sustainable. A lot of royals, especially poorer, relied upon grace-and-favor apartments for living (such as Louise of Hesse-Kassel's family).
Besides things like civil lists, how else might a royal support themselves? Besides income from civil lists, income as a rentier, were there any other ways they could make money? Could they improve upon the money they had through investing it in business ventures? Did royals get involved in business like stocks and other risky business ventures?
I'm mulling over ideas for my TL with Princess Charlotte, and the late Hannoverians were hated for their debts. It seems that besides the sovereign the minor royals were almost reliant upon their Parliamentary Annuities, and I'm wondering if Charlotte, now married, might see her grow through wise investments by her husband rather than it being wasted away through her (typical) Hannoverian taste for luxuries. I like the idea of her Prussian husband attempting to increase their money in some way rather than allowing them to rack up huge debts.