I've been on both sides of this subject;
When I was 20 yrs old and first married, I didn't want any children at all. I'm admittedly a person without a lot of patience (although over the years, I've developed a LOT of patience. lol), I never liked kids AT ALL when I was growing up, I was never one of those teenagers who babysat, I really couldn't stand little kids or babies!! LOL
Within a few years I changed my mind, though. We owned a home, had no monthly bills except mortgage and household expenses, and we could live on just my husband's salary. Well.... we decided to have a baby.... and that lead to 4 years of infertility treaments, tests, pills, temperature-taking, surgeries, etc. I finally got pregnant after a few years, but then had a miscarriage. I decided to stop trying to get pregnant altogether. Within 6 months I was pregnant again (this time without "trying"...no pills, no keeping track of ovulation....NOTHING). 9 months later I had DS15. Three years later I had DS12.
If I hadn't gotten pregnant afterall, we would've adjusted to life without children. When we realized that there was a very real possibility that we'd never have any children, we sat down and re-examined our plans for ourselves and our future; we made plans to take our money and invest it in real estate properties and then just enjoy life to the fullest as best we could. (and maybe even look into adoption somewhere down the line).
Anyway... I just want to say that just because you don't want any kids NOW (which is a good thing, by the way!!), it doesn't necessarily mean you will always feel that way. I never thought I'd *want* kids of my own, but I love my 2 DSs and am very grateful to have them.