I don't know about the "one and done" thing since I believe differently than most women with regards to family planning. However, I can address the fear of loving more than one. I can 100% guarantee you that you would love another child every bit as much as the first. I have four and I love each one of them tremendously. I love how different and unique each one is. I love watching them play together. My two oldest are best friends (of course they are only 6 and 4 so...).
As far as money- we live on one income, and it's a teachers income so it isn't a lot. We manage just fine and we have four children. True, we don't have all the "latest and greatest," but we have everything we need and then some. How could I ever compare having a child to having some material possession or fading experience? Giving life to someone- a whole new being- is amazing and miraculous and you could never put a price on that.
And the birth- for many women, the first birth is the hardest. True, there are always exceptions. My first birth wasn't bad, but my second birth was very traumatic and ended in a c-section. My third birth was a fantastic VBAC and was a very healing experience. I do work with ICAN (international cesarean awareness network) and many of the moms that come through the group here find that their VBAC empowers them as women and mothers.
Just my two cents and food for thought maybe. I don't know how old you are, but I know many young women regret the permanent decisions that make. It's impossible to know how you will feel 2 or 3 or 5 years down the road. I know I am not the same person I was 5 years ago. My desires and wants 5 years ago are different than my desires and wants now.