Getting to Know NYC Mayor Mike Bloomberg

Building on the legacy of Rudolph Giuliani is not an easy undertaking. But that's what New York City Mayor Michael Bloomberg — a billionaire with no government experience — was elected to do.

In his first in-depth national television interview since being elected mayor, Bloomberg tells 20/20's Barbara Walters who he is, how he's gotten so far, and what his plan is for a city that was shattered on Sept. 11.

Following are excerpts from the interview, which will air tonight at 10 p.m. ET.

ABCNEWS' Barbara Walters: Mr. Mayor, up until now, you've had the kind of life that most people dream about: fabulously wealthy, five beautiful homes around the world … Why in the world would you want to give that up? Why did you want to be mayor? New York City Mayor Michael Bloomberg: Because you get a chance to change the world, you get a chance to make a difference. I always find that question to a be a funny question: Why would you not want to have the greatest job arguably in the whole world?

Walters: Are there Bloomberg's rules for success that anyone can follow?

Bloomberg: Work hard. The harder you work, the luckier you get, it's amazing. I've always thought that a lot of my success was I just came in earlier and I stayed later. I cared more, I focused, and that's one of the things. The second is working collaboratively. I don't know any job — yours, mine, anybody else's — where you don't need other people. My lecture to kids is get rid of the words "I" and "me" and replace them with the words "we" and "us." You need to do things together. And the last thing centers around honesty. Being honest to others, it's obvious why. But being honest to yourself as well … You are who you are and then make the most of it. Don't try to be somebody that you don't have the skills to be.

Walters: Do you have a temper?

Bloomberg: Yeah, sure. I've never liked anybody that didn't. We all have tempers. If you don't have a temper, you don't have any passion.

Walters: What was the best time in your life?

Bloomberg: Well, the best time in my life, I suppose, was watching my kids grow up. I don't think just when they were born, but when they really turned into independent thinking human beings. When you say something to them and they say something back that you realize isn't repeating what you said, but an independent thought.

Walters: Sept. 11 came right in the midst of the campaign. Did you ever have second thoughts after that?

Bloomberg: No, all the more reason to run because it was obvious the challenge of pulling the city together and dealing with the economic results of that terrorism would be much more daunting, much more challenging. And if I could make a difference, it would be more valuable to the public.

Walters: You spent almost $70 million of your own money to become mayor … How do you answer the criticism that you bought this election?

Bloomberg: Well, the public can't be bought. What you can do is use the money to get your message out. A total outsider that the media doesn't know, in a media-sensitive town like New York, has to have a lot of money or you just can't be noticed and people can't find out the differences between what you would do and the person you're running against. The way I look at it is: I think I can make a difference. I did spend my own money, which means I'm not beholden to anybody and I can probably do a better job.