How Did Past Nobles & Royals Earn Their Living?
 

I'm a big fan of watching movies with old English settings, such as literature adaptation films (Pride and Prejudice, Jane Eyre, etc), even Sherlock Holmes and Wolfman (2010).

I'm always fascinated with the life of the nobles depicted in those movies; living in a huge mansion, dining with formal attire on, surrounded by full time servants who live within the compound (such as in Brideshead or Downton Abbey). So from where I see in them, they seem to live a life of eternal financial security.

I was wondering, how did (or do) the nobles earn their living?

As far as I know, they have land that they lease it to the peasants/farmer surrounding their territory. But is that all?

I imagine if the nobles and royals are still widely prevalent in current time, most of them would be listed in Forbes 400 of richest individuals or something.

Most of the original wealth came from the ownership of the land and the rents etc that the peasants, or others, paid for the land.

When the Industrial Revolution came along many of them invested in factories etc to diversify their income stream.

They also invested in other wealth creation.

The Princely House of Thurn and Taxis made their money by having an almost monopoly over the postal service of the Holy Roman Empire.

Land=Wealth was the basic formula. Also there was no such thing as the minimum wage so all those servants were paid what the nobles thought they were worth. Good, high ranking servants were well paid or not depending on how genrous their masters were.
By the 18th/19th century many of the British nobles were becoming poorer because of new taxes etc. So they found a new source of income, rich heiress'. Suprising how good a miners daughter or an american can look when she comes with lots of cash. In Downton Abbey that you mentioned, the Countess is an American who came with a huge dowry.
Some of the European nobles, like the Thurn und taxis earned their money through business but most were huge landowners. Even today some of the families still own vast tracts of progitable farming and timber. The Lippes come to mind (though the socialist govt. in that german state is trying to steal their land in the name of conservation).

didn't some of the royals rely on queen victoria for money

In the beginning of her reign QV was herself quite poor, most of the families wealth came from an injeritance from some really rich bloke who had a fascination with QV. She may have supported some of her relatives, like the Tecks and Battenbergs but I don't think she supported any of the general nobility.

Don't forget investing in privateer ships, Privateer - Wikipedia, the free encyclopedia
And of course trading with India and the Far East. http://en.wikipedia.org/wiki/East_India_Company

This is very interesting. Can you share the source of this?

I've read somewhere that nobles and royals were 'forbidden' to work to earn money. Is that true to some extent?

Not forbidden ny a law or anything just that they looked down upon people in 'trade'.

Most QV biographies will mention it.

According to this book review, The Mystery of Princess Louise: Queen Victoria's Rebellious Daughter by Lucinda Hawksley – review | Books | The Guardian , she insisted on being paid for her work, so most likely she was.