彼は昔より裕福だ。

English Translation

He is better off than he used to be.

“He is better off” doesn’t necessarily mean that he has more money. This is shown by the natural response to “He is better off than he used to be”, if that is all there is to go on, would be: “In what way?” It might be that he now has a less demanding job or that his commute to work is easier or that his grown-up children have finally left home! So I think a better English translation would be: “He has more money now.”

As a Native English and Japanese speaker I’d recommend: “He has more money than in the past.” because 昔 means past.