If you are wealthy, in a stable marriage, and knowledgeable about parenting, then I would expect children to be net-positive for your well-being.

Yes. You should be able to easily take care about yourself (financially, logistically, emotionally), before you accept the burden of taking care about someone else who cannot reciprocate in the following few years.

Imagine that you have less time, less energy, and less money; every day, for the following few years. Plus some unexpected problems appearing randomly. This is how it is when you have a baby.

In return you get a cute little person that is similar to you, loves you more or less unconditionally (unless you really screw up), and "becomes stronger" visibly every month. That can be hugely emotionally rewarding.

However, that emotional reward doesn't change the fact that you still have less time, less energy, and less money. So if something was a problem before, it will become much greater problem with the baby. That also includes the possible problems with the relationship: now the partners have more stress, and less time to talk or have sex (which are the two typical methods to solve interpersonal problems).