Only time I ask for a loan is with my sims who aren't of good moral character. So I definitely won't rush to pay it back. Have yet to see any tangible consequences.
If you don't have the patience for the Money Tree, there's also the Wishing Well(Romantic Garden Stuff), but that does come with quite the risk.
If you as a player have a certain questionable set of morals(and have Seasons), I recommend setting up a holiday that includes the arrival of gnomes. When they appear, you can go into buy mode and sell them. They do net you some decent cash.