Odds of Getting In
It's a blue collar field with steady job growth. But, you also probably won't be hired straight out of high school or vocational school unless you can demonstrate you've mastered the necessary skills. If you're just coming out of high school, you're going to need to participate in some sort of internship or apprenticeship program.
You will not be making a lot of money. Basically, you'll be a paid trainee. Get used to the taste of Easy Mac.
However, there are a lot of things you can do to make the first hire a little easier, and the first paycheck a little less cringe-inducing.
Earning a degree is important. Most welding programs last two years and are offered through community colleges or technical schools. You can earn an associate's degree in welding technology, or there are also several colleges which offer four-year degrees in welding engineering technology. This degree includes coursework in physics, chemistry, calculus, and computers.
Holding a degree makes you a lot more employable. Eighty-seven percent of graduates from one of the country's top welding schools, the Hobart Institute of Welding Technology, find jobs right out of college (source).
It's a skilled craft, so if you can demonstrate that you've got the skills, you should eventually be able to find a decent job.