M.T.
All kids like to be the center of attention, and most of them adjust really well to having a sibling. I have two kids and would have liked another, I can't imagine only having had one, I didn't have the desire for just one. However, not all only children are unhappy about it. My husband grew up as an only child and never felt a longing for a sibling as a child.
I wouldn't let having to work keep me from having another child. I was always a working mom, my babies were in daycare, and it didn't upset me. However, if you truly can't afford another child, then it's responIsible not to have one. I don't know how old your child is, but mine are 10 and 14, and they are expensive ... and college is coming in a few short years.
However, is it necessary to make a final decision about not having any more children now? I'm not sure your age or the age of your son, but it's okay to space kids more than just 2 or 3 years apart. You may opt not to have another baby now, but perhaps in a couple of years, you can revisit this issue.
Also, as amazing as your child is, and you may think another won't compare, the next child would be just as incredible but in his or her own way
Good luck