Odds of Getting In
Here's the cold, hard truth: there are approximately 6,500 people in the United States working as demolition contractors. That's crazy low. There are very few professions where the total number of people working the gig is fewer than at least five digits.
And—as you probably guessed from the phrase "cold, hard truth"—the news doesn't get better. With such a small job market, there's only room for a couple hundred more people in this career per year.
You can up your odds a bit by having some certifications and experience under your belt, or by knowing people in the industry who'd be willing to take you on. You could also hope for a series of unfortunate on-the-job accidents to wipe out most of the demolition contractors today, but that would make you a terrible person, wouldn't it?