H.J.
We just decided to have our third child. After two kids, lots of people asked if we were done or if we would have more...so I spoke to lots of moms about this.
The general consensus was that when you are done you know it. If someone asks if you want to have more kids you will say 'no.' If you say 'maybe' then you are probably not done and you really do want to have more.
As for our own personal decision, I knew in my heart that I wanted more kids, but I kept thinking about the practicality of it all...(new car, change in bedrooms, longer before I went back to work....) But in the end, we realized that all of that is short term and what mattered is what we wanted for our family!
As for the financial part, don't worry about that. You will never feel financially ready for one child, let alone multiple. Just set your priorities and don't let the worry of money stop you.
Good luck with your decision!