One thing that I found useful in making money is to not buy a scarecrow…

One thing that I found useful in making money is to not buy a scarecrow because for every bird that comes and you shoot you get 50 coins. Also when the rats come up let them stop and eat one of your least expensive plants or any plant for that matter before you scare them away, this also gives you 50 coins. If you keep doing this it adds up and can help you advance faster.