As for the income, the nobles were basically bussines magnates managing assets. They would have a well paid government job in the first place, and land, and maybe a business. There were taxes to be collected sometimes, there would be people who'd owe services, but mostly the land could be distributed further to tenant farmers and rent would be collected. The most loyal to the king could also get bonuses. In 11th century William the Conqueror and his men came from Normandy (nowadays France) to take over England for ever. William gave about half the land to his most loyal men, 170 Normans, making them "barons". In the 16th century Henry VIII dissolved the monasteries and appropriated vast amounts of property, some of which he would hand out as rewards to loyal men, along with titles.

A good example of a noble's career would be the Spencer family (princess Diana's ancestors). The first Spencers were 15th century feudal landlords. They traded livestock and other gifts of the land in order to buy more land. A knighthood arrived in 16th century, then an election to represent the shire as member of the Parliament. They were basically very successful and influential farmers. And because they were very good at it, they got more influence, and titles. In the 17th century Sir Spencer was made baron and was reputedly the richest man in England. Not bad for a sheep farmer. Not only the head of the family but also the sons would receive titles in their own right - one was made an Earl and the other a Viscount. A few Spencers became politicians, one was a Home Secretary, another was Chancellor of the Exchequer (head of government finances). Today they have a descendent who is a Duke.

"Earl" is the oldest of the titles, having existed in Anglo-Saxon times. Initially, and earl would be the local ruler of an area, something like a provincial governor. They collected taxes on behalf of the king but were allowed to keep some.

Big changes happened with the arrival of William the Conqueror. He was famous for making everything neat, tidy and efficient. And since the Normans didn't want to deal with local opposition, the English nobility was gradually limited in influence and subsequently replaced with Normans altogether. An earl's dominion would become smaller, with less land and less influence.

In the meantime, William declared that all land was owned by the king. His fellow men who helped him with victory got large parcels of land and the title of "baron". The barons had to attend the King's Council. In 13th century the barons had so much power and riches that they tried to rival the king and even make him share power - thus Magna Charta was created.

"Duke" signified Sovereign status as William the Conqueror was Duke of Normandy. As a title in England it appeared in 14th century, when Edward III created it for his son. The rank, of course, had to go above "baron" as you can't have nobles more powerful than the king's heir. Dukes are usually either royals or somebody really close to them. After all the trouble with the barons, the English kings never created many dukes.

The title of "Marquess" is not particularly popular in England, due to some controversies surrounding its early holders. A new title was simply a way for the king to show appreciation and provide certain status for their favourites.

"Viscount" is influenced by the titles in continental Europe and appeared after Henry VI was crowned "King of England and France". The viscounts were originally the sheriffs of a county, which meant a high ranking local official, something like an estate manager or magistrate.

Have a look at what /u/chodo-shaggins- wrote last summer in response to Did members of the peerage, e.g. the Duke of Cambridge, need to live in the city/territory they were Duke of or were these titles just a status symbols?