It used to be if you wanted to break into broadcast media you first had to start small – by getting a job as a correspondent at a local news station and then working your way up to bigger and bigger markets.

That's the career trajectory that Casey Keirnan followed. He started out covering high school sports in small towns and then eventually landed a job at CBS Interactive, which was trying to create an ESPN competitor for OTT streaming. But after only two years on the job, Casey's contract wasn't renewed, and he feared he would have to go back to local news.

But then he launched A.M. Hoops, an NBA-focused YouTube channel that ended up being so successful that he replaced his previous salary within a few months. Today, it boasts over 400,000 subscribers and 264 million channel views.

In our interview, Casey told me about his slow climb in local news, why he struggled at his CBS job, and what inspired him to strike off on his own to start a YouTube channel.