Starting a podcast and building authority within your specific niche is an exciting way to grow a personal audience of listeners who regularly engage with your content. Since Apple's podcast store has a built-in audience and ranking system, you may be able to launch your podcast with a high volume of listeners. If that's the case, you'll rise to the top of the rankings and gain a huge amount of exposure.
I created an “Every Day I’m Hustling” shirt and sold enough for the campaign to ship, but didn’t earn much on the experiment because of some not-very-effective Facebook advertising. Still, some opportunity here and a friend of mine is doing REALLY well with this. If you can create awesome designs and reach the right people with good Facebook targeting, Teespring can be very profitable.