To climb Mount Everest you will need plenty of high altitude climbing experience before any company will sign you up to there team. You will also need very deep pockets to pay for your climb too!
I would suggest to go out and try climbing, see if you like it and how you cope. Take a look at the articles about climbing Mount Everest at the link below.
You can read a great article about Mount Rainier at the other link below.
Remember, climbing can be dangerous so it is important that you have the right gear.