What is the difference between 賺錢 and 掙錢？
I'd like to make a supplement based upon previous answers:

Usually, 挣钱 and 赚钱 are exactly the same. But in some special cases, 挣钱 could reflect a scenario of hard working, since making money is not easy, while 赚钱 could mean that making money is easy, compared with 挣钱. 

Here, the verb 挣 sounds like you have to make great effort to, you can see the verb 挣扎, which means struggle. The verb 赚 means making a profit, it can also be used as an adjective.

So we have the following phrases: 努力挣钱，working hard to make money (though 努力赚钱 is also possible) and 躺着赚钱, making money while lying on the bed.