A lot of the people who climb Everest these days are quite inexperienced. With the proper equipment and a high fitness level, along with lucky weather and a boatload of cash, pretty much anybody can climb it. For this reason, amongst true mountaineers, a guided climb of Everest along the normal routes is not considered an accomplishment.
As for an idea of costs, to properly equip yourself for the climb, you will need to spend upwards of US $5000 on top-notch sleeping bag, boots, clothing and other equipment. But that's just the beginning. Aside from travel costs to get to Nepal, a guided climb up Everest can exceed $40,000.
How do you pay for this? If you can't pocket it yourself, sponsorship is an option, but acquiring it requires you either be famous to begin with (with a long string of mountaineering accomplishments), or come up with some goofy gimmick, which unfortunately seems to be a continuing trend on that mountain. Youngest, oldest, one leg, no eyes, climbing up in cotton underwear, etc. If you're creative enough, and it hasn't been done yet, maybe you could find somebody to sponsor you. To seek a sponsor, the key is convincing them that it would be money well spent in promoting whatever it is that they're selling.
To train for the mountain would require attaining a high level of general fitness and endurance. Take up marathon running, do core workouts, take long backpacking trips over steep terrain while carrying a heavy pack. It also wouldn't hurt if you had some training in ice axe technique, glacier travel, and general high-altitude mountaineering. But like I said, a lot of people arrive there having never climbed a serious mountain before. But take heed, the high altitude and severe weather are no joke, and lack of experience increases the odds that something untoward may happen.