What is a one-sentence summary of the following article?
When you land on the space, you may choose to purchase the property at the price listed on the card.  Pay that cost to the banker or the owner of the property.  If you do not purchase the property, and it is not currently owned by another player, the banker will hold an auction.  You can participate in the auction even though you chose not to buy it at the purchase price. Once you own all of the site properties of one color, you have a monopoly and can build on them. You can charge rent from other players who land on your property. When you own utilities, you can charge usage fees.  Players who land on your utility will owe you rent based on a dice roll.  Owning both the phone and internet utilities will greatly increase your income from other players.  A player who lands on your utility will owe rent determined by the amount they roll on the dice multiplied by 4, then multiplied again by 10,000. If you own both utilities, the rent owed is the player’s dice roll multiplied by 10, then 10,000. Airports allow you to collect fees from other players.  Each time a player lands on one of your airports, they will owe you the amount shown on the Title Deed card. This can be any number you negotiate together. If you have any buildings on properties of the same color, you cannot sell the property until you sell all of the buildings on that same color. You will receive half of the purchase price listed on the deed card when you sell the house back to the bank.  You can sell on your turn or between other player’s turns. You must sell houses in even numbers the same way they were bought. You can receive half go the deed price for the hotel or trade it in for houses equaling the same value. For instance a hotel can be sold to the bank and you can receive 4 houses from the bank to put on that property. You can sell sites, airports and utilities to other players to gain money.  The price they pay you is any amount agreed on by both parties.  Sites can’t be sold if there are buildings on any of the sites in that color group.  You must first sell those properties to the bank. You cannot sell houses or hotels to other players, only the bank.

Summary:
Purchase a property. Own utilities. Buy airports. Sell property to other players at an agreed upon price. Sell houses to the bank. Sell hotels to the bank. Sell property to other players.