I train service dogs, and I'll tell you that nobody does it for the money.
I've talked to lots of organizations, and while it varies a little bit based on location, most organizations pay apprentices $20-$25K. Training directors with a ton of experience will usually make around $35-$40K. You'll also work a lot of extra hours without overtime pay (last week I worked 62 hours, though usually I work about 45). Benefits (insurance and such) are not very good, especially if you're used to working with a large company. And of course it's physically strenuous.
Of course there are a lot of perks; we do most of our shopping during the work day because the dogs have to have practice working in public. My personal favorite is the mandatory "movie theater" outing... dogs HAVE to learn to sit quietly through an entire movie.
Now, I personally, can't see myself doing anything BUT training service dogs in the future, I absolutely LOVE my job. But it's something I've dreamed about since I was 12, and worked toward my entire adult life. We have had trainers start working here just because they think it'd be a fun change or something, and they end up not staying for long because you have to really have the drive for it to stick with it.
Like someone said above, the best thing to do is to start volunteering for a service dog organization. We work with so many volunteers, we can tell within a few days of working with you whether you would be worth hiring.
And we'd always rather hire a long-time volunteer, rather than someone we've never worked with. Most organizations have very few openings for trainers, but have more openings for kennel techs - the people who take care of the health, hygene, and physical well-being of the dogs (feeding, medicating, cleaning, exercising, grooming, etc.) - so that would be a good place for you to start. Those jobs are usually part-time and pay less than a trainer, but it's a great way to get your foot in the door. We hired a kennel tech last year and promoted her to trainer after only about 3 months, because we saw that she was talented... we didn't even officially have a trainer position open when we promoted her.
If volunteering is not an option, getting training experience through other means is always a good idea. You can apprentice with a trainer in your area, or with Petsmart. While you're working, you should read all the training books you can get your hands on, go to seminars, and get a
certification.
Good luck!