Love (the hearts) are very useful. Love boosts your profits if you have enough of it. Love upgrades get progressively more expensive with each purchase. They are also very useful as each new purchase doubles the profit bonus you get for each heart you have. You can earn love by switching buildings between them, from briefcases, or in gifts that your friends send. The easiest and fastest way to get hearts is by switching buildings between them. Do not upgrade your Love as soon as you have the required number of hearts, because you will not gain much. Only upgrade when it is most convenient in terms of gains. Connect to Facebook and add friends to gain hearts. Each time you switch a building in your city with one in your inventory, you will earn a specific amount of Hearts. After switching buildings, you will start from the beginning. You will have to go through the Power and Construction upgrades again, but the bonus in profits you get for all your buildings will help you progress faster. Ensure that you have enough money saved before making the switch to unlock at least the first Power level so you do not have to tap to collect profits.