I like the game, and I am hoping that if I buy the game I get the game and won't keep having to pay money for it or for extra features.
WoW has a monthly fee. You will have to continue paying the monthly fee if you want to continue playing. However it does have a free to play option with added limitations, this is called the Starter Edition.
You mentioned in your other question that you have some kind of a limited internet access. Keep in mind that the Starter edition would be a very large download. Additionally, there are occasional updates to the game client that require large downloads. This may mean you would have additional costs associated with playing WoW.
When you buy all the sets (the expansions and all the stuff that require for you to play) you just have to pay a fee every month.
To be able to play and log into the game, you don't need to pay anything else except the fee every month. Also there are other payment plans that cost a bit less than the monthly renewal.