As it has been written by other guys - it will come naturally during the game, but... if you would like to "generate" some money - you can use small glitch in the game.
Just before first shop in Forest Grove you will have to fight with wolves. After finish fight you can also get some money thanks to flower cutting.
Then do following steps:
- enter to the shop
- go to improvements and go out from it (you can buy something if you want).
- you will see saving icon (then the game is saving information about money and improvements)
- leave shop
- leave game
- go back to game using "Continue"
then you will be again before the fight (with respawned flowers additionally) with updated amount of money - the same as it was after leaving shop. Also purchased improvements will stay with you.
Now you can fight again and cut flowers to get new money.
Using that glitch several times you can boost your amount of money (one fight + cutting flowers should give you around 150 - 200 coins).
The same glitch you have each time of shopping, but first shop in Forest Grove seems to be the fastest and easiest