Money can be earned in many ways in PvZ. Minigames, Co-op Bowling, Adventure mode (Drops + end of level bonuses), the Zen Garden and more.
The shop unlocks shortly into Adventure mode, and by the end you should be getting close to obtaining this if you haven't already
To unlock this trophy spend a cumulative total of $25,000 on anything from Crazy Daves' trunk (This includes the slots for extra plants).
Your trophy should unlock as soon as you make the purchase to take you over.