Um, depends on how you define making money. Is $60K making money? What if I told you that the author puts in less than 5 hours a month to make $60K a year? Is that making money?
If that is your definition, then the answer is "everything". If your definition is "lots of money" then the answer is, as always, very few things which are a lot of hard work.
Tell us more about that 5 hour per month thing, please. You know, a lot of people from developing countries, including myself, find $60k a very big pile of money.
That person makes $60K/year from 5hours/month but you can't imitate him. It's not really time = money. He is using some kind of personal/company brand that took years to build. There is value, but it's not in the time he is putting.
Okay. An example: Spend 10 years building knowledge and reputation on some field and become really good at it. Then give a one monthly paid talk at some conferences. That goes $5K/talk. Pretty much achievable. You can even make more, depending on the experience and value you bring.
Step 1: Find problem/customers and figure out how to use google to get them to you
Step 2: Solve problem in a high-quality, maintainable, relatively bug-free way
Step 3: Charge a lot (so you don't need as many customers)
Except to add new features, you can literally watch the money roll in since you've somewhat automated getting the customers. And don't do stupid things like iPhone apps.
If that is your definition, then the answer is "everything". If your definition is "lots of money" then the answer is, as always, very few things which are a lot of hard work.