I'm also with keepingup in the 'you can never be prepared...
I've spent my whole working life working with kids and had always been around babies and toddlers as a child. I thought I was prepared. How wrong was I....
I got the baby that screamed endlessly in the early days, the baby that was desperate to run, nevermind walk from day 1, He has been bloody hard work. He was desperately wanted and the result of IVF and i've felt guilty on some of the torturous days and really beat myself up about not enjoying him. Don't get me wrong, I absolutely adore him and the days are getting easier now he's not as frustrated but absolutely nothing could have prepared me for life as a new mum simply because no 2 babies are the same.
All of my friends who have babies of a similar age have had different 'issues' with their little ones - some have simply refused to sleep beyond an hour or so, some have had reflux and other tummy troubles (DS included), some have just been so inconsistent in what they do that mums have struggled to make any sort of routine.
Gonewiththewind is also correct - there is never a right time. A friend of mine said she wanted to wait til after her 30th so she could have a drink (or several bottles) on her bday and now that's passed she's now saying she might wait til her sister has got engaged so she can have a drink there - my point is, ther'll always be something coming up as a reason to wait til after it. Also, you'll never 'afford' children as such - you'll spend within your means and provide as best you can and make cuts in ither places when necessary.
I say, you're ready when BOTH of you can honestly say, 'if I was pregnant would we be ok with it'? Til then, practice! :-D