The land market within Second Life is a rollercoaster at times, but when it's stable it is obviously a great business. It is not, however, easy. Much of this has been earlier in this document, but not in the context of a business.
There are many variables and risks associated with the Mainland (no Covenant) land market at any given time:
Land Auctions: Linden Lab auctions off simulators people can bid on (https://secure-web6.Second Life.com/auctions). Bidding on a simulator is not a cheap prospect, and can be a liability if there are many simulators being auctioned at the same time. This can increase one's tier while not increasing one's revenue.
Market Price: The market price per square meter of land fluctuates, but it can suddenly dive if someone decides to dump land on the market for whatever reason. When many people dump at the same time, the results can cause a crash. Other people, seeing low prices, get worried and dump their land at a low cost as well. This run on the market can be devastating if you don't pay attention and find out why it is happening.
Global Time: Knowing when the market is active is important. Many seasoned land dealers will refer to Europe and the United States separately, as the people from different parts of the world generally buy at different times.
Swoop Risk: Mistakes happen, and "swoopers" will often dive in and catch a piece of land you accidentally mispriced. They may not give it back if they don't ...