A lot of truths about photography are hard to hear when you're looking at making a career out of it, but they are necessary if you want to go into the profession with a complete understanding of what's to come.
This is one of the few videos by First Man Photography that I don't agree with all that is said, however, the underlining sentiment is important. That is, selling prints of your photography is damned hard. I have had some success in this area and even more failures. Like stock photography, the abundance of images now readily available has flooded the market with such a level of supply, there will never be enough demand. This doesn't prohibit success, it just lowers the chance of it drastically.
When I first started to make money in photography, I tried to sell every image on every platform and service I could find. It was a truly ridiculous undertaking and one that proved to be of limited value to me. Then, I made a small change some years later, and saw far more success. I decided rather than casting the widest of nets and hoping to catch something, I'd specialize and market specific images for specific purposes. This led to me making some sizable sales and rewarded my efforts substantially more than anything did before that.
The advice in the video is similar towards to end and I would echo it: work out which images you want to sell, who your target market is, and how you're going to get the images in front of them. Spreadbetting is rarely rewarded in such a saturated market.