Is there a single word for "money-mindedness"?

Solution 1:

Mercenary comes to mind
But there are more:

acquisitive, avaricious, bribable, corrupt, covetous, grabby, grasping, miserly, money-grubbing, selfish, sordid, stingy, unethical, unprincipled, unscrupulous, venal

Solution 2:

pecunious

Etymology: < Middle French pécunieux (c1370 as peccunieux in sense 1, 1498 as pecunieulx (plural) in the passage translated in quot. 1509 at sense 2; French pécunieux, now rare) and its etymon classical Latin pecūniōsus well provided with money, moneyed < pecūnia money (see pecunial adj.) + -ōsus -ous suffix.

The negative impecunious adj. is much more used.

1. Well provided with money; moneyed, wealthy.
2. Money-loving, avaricious; miserly, ungenerous; (also) frugal, thrifty.

Solution 3:

"stingy" or "miserly" might be appropriate if the context refers to a motive not to spend money.

I'd use "greedy" if the motive was to acquire more money when the individual was already rich (and clearly didn't need the money).

"mercenary" would perhaps be better if the person was doing something only for the purpose of money, and not caring about other consequences.