[The Fifth Horseman]

Then you were doing something wrong.

Run the game in DOSBox.
Open up Cheat Engine and choose DOSBox as the process to work on.

Choose First search. The money is most likely stored as an 8 byte value.

Do some stuff in the game as long as it doesn't change your money. In CE, choose "unchanged value", then "next scan".
Repeat this process a few times.

Do something that lowers the money. In CE, choose "decreased value" then "next scan".
Repeat this several times as well.

Finally, do something that increases the money. In CE, choose "increased value", then "next scan".

After a few repeats, you should have a very small list of offsets to choose from - ideally only one.

Double-click that offset on the search list to make it appear in the bottom list. You can change its value or freeze it to make it unmodifiable by the game.