To earn money as fast as possible, have at least $5,000. Purchase 25 Love Potions and 15 of any other potion. Set the potion price to the max for each one. Now go to the "advertising" tab and set your daily advertising costs to $30. Start the day. Depending on the percentages of broken hearts, combustion, etc... you can earn up to @1500 in profits this way.
(If all the chances are low, lower the advertising costs to $10).