20-Year Prospect
The Internet changed everything we thought we knew about watching cat videos. Before it, you had to film your own cats, and then hope for the best. That's just madness. Surprisingly enough, it's changed a few non-feline things, too. Ask anyone working in print media about it and watch them start to panic. Seriously, it's fun.
The print media (by which we mean newspapers, magazines, and books) is hilariously inefficient by modern standards. This is why all of these things are increasingly being done digitally nowadays. Even the mighty crossword puzzle has been digitized. Once it was a staple of the newspaper, now it's a feature on a website...and an easily-made feature at that. Anyone can enter words and clues into a free web-app and get a crossword puzzle made for free.
Another big problem is that most of the fans of crosswords are getting older (source). In the olden days, a crossword was something you could stumble across in the newspaper or in a magazine. Now you have to seek them out, which makes it harder to gain new fans.
There are still devotees, as there always will be...but the fact is that, there are very few people who can make a living making crossword puzzles. One such writer estimates only 150 of them are out there. Even now it's barely a viable career.
Unless there's some crazy-crossword-hipster group that springs up in the next twenty years, your chances to make money doing this are pretty slim to none.