The usual critique of this type of card is that it is overpowered once the curses are out. Even if it's 'Gain a curse, if you do . . . ', it can be OP if you can easily get rid of the curse. If it has negative VP, it can be OP if you can trash it near the end of the game or give it to your opponent via Ambassador/Masquerade.
But what about this:
Loanshark Reaction $6
(-5) VP
When you gain this, place it on your Loanshark mat. If you do, gain 3 Golds. Return all Loansharks on your mat to your deck at the end of the game.
While this is set aside, during your Action phase, you may place any number of Golds on your Loanshark mat. If there are 4 Golds on the mat, return them and one Loanshark to the supply, and gain a Province.
So, this card gives you -5 VP and can't be trashed, Ambassadored, Masqueraded, or Trader-ed. The bonus for paying back the loan is good enough that you'll consider doing it over just buying a Province with your Gold. Plus, at $6, you can't open with it, barring Baker.
Would anyone buy this card over straight-up Gold? Is it OP?