Gold Thumb
Someone who is very good at making money. One who is extremely successful in their financial endeavors. Like the term green thumb, which is someone who is good at growing plants, someone with a gold thumb is good at growing wealth.
I have made a profit on every stock I have ever purchased. They say that I have a gold thumb.

Wow, Carter just opened that carwash last month, and it’s already turning a profit. Boys got a gold thumb.