From Second Life Wiki
You have several options in purchasing land, depending on how you want to use your land and how you want to pay for it.
Payment by credit card or PayPal
You can use our regular land purchase mechanisms.
If you want to maintain a high level of control over who can access your land, you want a private island. You'll want to place it with no adjacent land to provide the most privacy. To buy an island, use the Land Store.
If you want a public space with a high level of interaction adjacent to other land, you may want to consider buying Mainland land. Mainland land ownership requires a Premium account ($9.95/month): Detailed information on Mainland land pricing: Land Pricing & Use Fees
Find out all the ways to acquire and use your [land].
All invoice orders for islands must go through our Special Order process. We require prepayment of 6 or 12 months of land fees to use invoice payment. Note that we require use of a credit card to authenticate the order, but the card will only be charged if you select that as the payment method.
Linden Lab accepts wire transfer for payment for land purchase (as well as for LindeX deposits). To order an island, first go to the Land Store and initiate a island order. Then go to the Wire Transfer page and provide your wire transfer information, select Earmark Funds?: Island Purchase and enter your land order number in the Notes field.
To credit your Second Life Account with Wire Transfer, simply fill out the form and enter Earmark Funds?: General Credit. You can use the funds deposited by wire transfer to bid for Mainland land in our Land Auctions.
Land on private estate(s)
Alternatively to buying land from Linden Lab, you can also buy or rent land from Private Estate Management Companies. No premium account is required in this case, saving you $9.95/month. Please read also the Land Buying FAQ for more details.