This topic came up because of a question posted by a reader. I will attempt to answer it briefly - though I may find I am doing Ryan's homework, it is too much fun to resist.
When you think about the 1800's remember that a peer would have one male heir. That heir would inherit most of the wealth, the estate, and most of the income, depending on what previous generations had arranged. So, indeed, in each generation, there would be a small number of rich landowners, who were peers. As Ryan suggested in his question on my last post.
This is the coat of arms of an earl.
Peers, did have a lot of responsibilities to their tenants. Making sure they implemented modern farming knowledge, and this was an age of enlightenment in terms of advances for both industry and agriculture. They were also like the millionaire playboys of today. Fast horses (instead of cars), gambling, and flashy women. They also employed a great many servants, which in itself was an obligation. Men of rank weren't expected to put on their own clothes etc.. If they did, they were doing someone out of a job.
Also, there were always more than one offspring to each noble couple. These were the days when contraception was sketchy at best. And while infant mortality was also high, families tended to be large. Which meant there were lots of other ladies and gentlemen of the aristocracy who were not major landowners or peers of the realm.
They had to work. So what did they do.
Now there is a great deal of information about this, and I am going to give you only a smidgen of it here. You will find examples of some of this in Jane Austen's various works and lots of detail in social history books.
This is the House of Lords in 1808-1811.
The heir, if he was titled, was expected to take his seat in the House of Lords. He was expected to make speeches and be a lawmaker. The relationship between the House of Lords and the House of Commons started to change around this time, but the Lords, (Dukes, Marquises, Earls, Viscounts, and Archbishops) had more of a role to play then than they do now.
The second, third and fourth... sons might receive some money set aside from their mother's marriage settlements, or even some funds she might have brought to the marriage. These funds they would be expected to manage through investments, in "the Funds" or perhaps they might bey property, but because they were gentlemen, they would not be farmers - not if they wanted to be taken seriously.
This is an officer in the fourteenth dragoons. 
There were careers that were considered suitable for a gentlemen, or a member of the aristocracy - the younger son of an earl for example. They might buy a commission in the military, starting with a cornetcy and working their way up. They could start higher. The higher the rank you bought the more it cost, and the greater the responsibility. In those days officers led from the front, and up close and persona, so they risked their lives for their country.
Similarly they might join the navy and rise from midshipman to Admiral, but they would never go as a common sailor.
I should mention that Britain was at war with France and Napoleon for a very long time during this period.
They might become ordained, so a vicar, or a parson. Church position, or livings as they were called, were often given out by the local Lord. So he might give one to a brother or a cousin. These men were still gentlemen, and they went to all the right parties, but tended to live in the country.
They might, if they had money, occupy there time dabbling in Science, inventing things. There were no research companies doing R & D, it was simply well educated men and those were usually the sons of noble houses or gentry, who had a thirst for discovery, natural history, archeology, science. If you look up inventions in this period you will start to see the beginnings of electricity, the steam engine, and of course the inventions that took us into the industrial revolutions.
Business was an acceptable occupation for a gentleman, provided he didn't talk about it. Poetry was also accepted, though they mostly did it for love not money. Look up Byron for example.
Here are the House of Commons in 1808. Still looking very gentlemanly, I would say. 
Politics in the House of Commons was also very acceptable, another way of governing the country and again, elections and voting were very different than today.
What wasn't acceptable was anything that smacked of the "shop" or "trade". So no gentleman would sell produce or product, or make saddles, for example. This would make him unacceptable to his equals. It would be considered scandalous.
In Jane Austen's P & P we have soldiers who are gentlemen, we have a parson, we have a great landowner, we see that Lizzie's uncle is a man in business and not quite so acceptable, to Mr. Darcy who looks down on Lizzie's family for their low connections.
Look for books like these:
THE BRITISH ARISTOCRACY
Mark Bence-Jones and Hugh Montgomery-Massingberd
Constable, 1979, ISBN: 0-09-461780-5.
THE AGE OF ARISTOCRACY, 1688-1830 ( Buy a new copy or Search for a used copy)
AUTHOR: William B. Willcox and Walter L. Arnstein
PUBLISHING DATA:
1. DC Heath and Company, 1992, ISBN: 0669397180.
2. Houghton Mifflin Company College Division, textbook paperback, 2000, ISBN: 0618001034.
You will find lots of information here for your Jane Austen reenactment Ryan.
The Jane Austen Centre In BathWell, this skims the surface and I could spend ages recommending books and posting links to great sites, but there are some on my website and lots more to be found surfing.
Ryan, I love the sound of what you are doing with your class. I would dearly love to hear all about it, and pictures too.
Until next time, Happy Rambles.
