Odds of Getting In
The odds of getting into any Special Forces Unit aren't great. When it comes to getting into Delta Force, you have to compete against other guys who think they're better than most of the Special Forces. It's like college entrance exams—with guns.
Some estimates place the amount of soldiers applying for Delta Force at 1,700 per year. Out of that number, less than thirty will make it through to OTC. Out of those thirty, another eighteen will drop out before completing their course. Another six won't pass the test after OTC and be required to take the entire course over. So six out of roughly 1,700 already-massively-elite people actually make it to Delta Force in a year.
You have a vastly better chance of winning an Olympic gold medal than making it into this group. We know we sound like your mother saying the same thing over and over, but those 1,700 applicants are other highly skilled soldiers. These guys are already Rambo. They just need to become Super-Rambo. (Not a real movie, by the way, so we won't link to it.)