I had my dc at the age of 22 & haven't had any more. I'm now 27 and my dc is 5. At the time we lived with parents so child minder costs were easy. Now we rent a house and I have just started a new career.
If we had another child say in a couple of years when I've got my feet under the table at my new job there is no way we could afford child minding fees plus rent and household bills. It would seem like 2 separate families already.
I still have time on my side, but it would be hard going to increase my salary so much that even in 10 years time it would be hard to pay all the costs. In 10 years time my parents will be retired and my mum says she could look after them whilst we both worked. That would be a huge age gap, plus I'd be relying them on staying in good health in their retirement. My mum is already having weight related knee trouble.
Maybe I should just accept we can only afford one child and be grateful for what we have? It's hard though when your biological clock is ticking