Land Type
There are two land types, PG and Mature. Like the movie rating system, PG means that no violence, sex or anything of the like can happen on that land. Mature means anything goes. Usually, the market will pay more for Mature Land, so look for steals of this land type if possible.

Terrain
Like in real life, the type of terrain surrounding your land is important. Land on the beach, on the edge of cliffs, islands and hilltops will sell for more than land that’s surrounded by landlocked, flat terrain.
Land that isn’t snow-covered will sell for more, usually. There are a few buyers in the market for snowy terrain.
Land that is underwater will sell very cheaply, for obvious reasons. Some people will even scam others by placing thick foliage on top of water covered land and then sell it as an island. If the water is shallow enough that it can be raised above the water line by terraforming, a hearty profit could be made from it.
There’s also nothing stopping you from building on top of the water and renting the space either. For someone not looking to spend upwards of $195 USD and all the $Ls required to buy an entire region, I would recommend underwater land as a good way to get some solid rental properties for a cheap price.

Location
Location, location, location. Where land is located in relation to telehubs also affects the purchase price. Businesses and event hosts will usually like to rent or buy up land close to telehubs so their customers can have easy access to their merchandise after teleporting. Farther away from the hubs, where there’s not as much lag, people will buy or rent smaller plots of land for their homes or personal sandboxes.

Network and Research
And never forget to tap your social network or to spend some time hunting through the land sales area. You can rely on your friends to let you know if they’ve found a good deal, and they’ll be more likely to sell to you at a lower price.
Land that is listed cheaply ($L 3 per sq. m) is usually being sold by someone looking to get out of the market. This is the bottom price you can expect to pay for land. Look for plots with the attractive qualities discussed above, and they should have potential for getting you a higher selling price.

Land baron
If you are absolutely serious about owning a lot of land and managing it, then go to the land auctions at http://secondlife.com/auctions/. You’ll find entire regions on sale for $USD 1000. If you sell off the smaller lots at market prices, you should clear around a 30% profit. Renting could work too, but it’ll be harder to attract renters and you’ll have to pay tier fees month after month. Sell it all, and you’ll just have to pay a month of tier fees and the rest of the Ls are yours.
Now, how do you sell all that land?