Others, such as Zephyr and Riotgirl have already touched on this in depth... financial responsibility vs financial independance. My own opinion is that any dominant should be financially responsible. As others have said, that means doing the best they can with what they have, they keep their bills paid, food on the table and the power turned on. They take care of life's necessities. I don't include credit scores or even debt in that because I've seen in my own family what unexpected medical bills can do to both credit scores and your debt level virtually over night. Its something you can't control and can't always be prepared for (even if you do have medical insurance, what happens when it runs out?).
Some would say financial responsibility has nothing to do with being a dominant, I disagree. How often in these forums have we talked about the importance of a dominant being responsible in play, in how they treat a submissive? Responsibility is a character trait, if one is responsible in their character, they tend to be responsible in all things that they do... play, money, jobs, etc. Its not that the money itself is important, but rather that financial responsibility indicates that dominant is likely to be responsible with other things in other areas.... say for example a submissive who's bound and helpless. It doesn't mean they are perfect, accidents happen... but its not our mistakes we are measured by, but what we do about them. And again we come back to responsibility... as in taking responsibility for our mistakes, our accidents.
As for low income dominants... I would suggest looking for two things. One would be financial responsibility in the situation they are presently in. The second would be some ambition to improve their current situation. I think those two traits, whether they are absent or present, say a lot about the character of the person.
A stern discipline pervades all nature, which is a little cruel so that it may be very kind - Edmund Spencer