How do I make a money system?

I am trying to make a tycoon game and of course i had to make a money system - but the thing is i dont know how. So what I basicly did was that when the costomer comes in and buys somthing i want to make a number counter that you can see change by the amont of money you get. If anyone could reach out to me it would help a lot.

The money amount would be a global variable and when customer purchases something you add to the global variable.

thanks. have a good day.

how would you display that number (sorry that it's been a couple hours.) for when they buy the item, I did the global variable and I want it to display the money that you get.

Using a Text object you set text to money where money is the variable. If you want to display the specific money amount you are adding then you'll have to pick it out from the events you are using and set another variable to that value and use set text to show variable2.