My boys are 2.5 years apart, and, although they are great little buddies, I know that it could possibly have been better if they were closer to 3-3.5 yrs apart. My next baby will be 22 mos younger than my 18 month old, and I know it will be more of a challenge.
That being said, there is no "right" answer to this question. My mother had my older brother and sister 18 mos apart, and then I came after another 18 mos. Between me and my next sibling there is just over 4 yrs. Somehow, those of us who are only 18 mos apart turned out better than my younger brothers who had more spacing :-) (Perhaps due to my parents being older and more tired with the youngest, or the fact that we older kids were their primary babysitters for much of their childhoods.)
There will never be enough money. There will never be enough time for everyone and everything that needs to be attended to. There will, however, be enough love to sustain your family if you are committed to it.