"When you get the money, the only thing you want to buy is time." – mike
How we spend time is how we earn time.
That statement seems counterintuitive on the surface, but let me explain:
If time is the only thing we have for sale, we are always in debt.
The only way to escape this paradigm is to make something that keeps working after we stop working:
Music, art, software, devices, services, books, movies, products — the list is quite literally endless.
Build once, sell twice.
The extent to which anything keeps working after you stop working determines how much time you earn from making it.