For your specific example, do:
Text->Set text to "Cash: " & money
Anything between " " will be displayed as you typed it.
Use & to join different things together
For global variables, just type the name without quotes e.g. money. For instance variables or object values, type the object name and variable/value separated by a dot e.g. Object.variableName
See the bit on Text (strings) in the manual on Expressions for more info.