Simple answer is that if it is in their heart's to be motivated to achieve greatness at business-like endeavors, they will be great. Or if they see it as a big step toward a greater dream, or to help a cause they love. However, even though they could be great with anything including money, usually amassing wealth is commonly not one of their life's aspirations, and some can be a bit disorganized regarding money matters, simply because they are not interested enough (this is not a weakness, or inherently "bad", but just who they are). So it is not so much that most INFPs are naturally "bad" nor industrious with money, but more than they don't care as much regarding these matters-at least not as much as other personality types perhaps would (we are not Js, to be sure.)
I strongly believe that INFPs can do whatever they desire, as long as their heart is in it. To be motivated to do something, you should just learn to see value in it, so that you put all your heart into it. Of course, this doesn't mean that money must be important to you, and if it isn't, that's perfectly OK. But we can indeed be good at most things, and should not feel limited by our beautiful personality type (INFPs can be business men/women, even though that might be a rare ocurrence given that what is usually expected of most business men/women often clashes with many INFPs values, although not necessarily so-INFPs should be free to be who they are, and so does everybody else.)
For the record, I am quite a "typical" INFP in that money is far from my priorities in life, thus I am not a great at making tons of money, nor being that organized with finances. Money just doesn't matter as much to me, save from its utility (I only need as much as I do to live under a roof and be comfortable.) I could do better, and we can all learn to also better manage our finances without betraying our values or losing ourselves. I would love to have more money but only to keep chasing after my dreams without worries. Otherwise, it has no inherent value to me-I do remind myself constantly that it is necessary to make money, if anything to keep chasing after my dream in a more comfy way; not because "I have to make lots of money" to be truly fulfilled/"successful" (of course, an idealist could be happy homeless too, but it's not a lifestyle that I envision/wish for myself.)
INFPs should also remember that even though we may often not mind as much about money or wealth, our views are not the only ones out there-let people care and strive for what they wish, even when we can't relate much to what's driving them. Not everybody that strives for money must do so for its own sake-there are those individuals that believe that stability is important for themselves and their children. It is perfectly OK and "natural" for them to seek this, even if such things may not personally be as important to us.
