I'm training my own. She is almost 10 months old now. Boston terrier(mostly)/fox terrier mix.
The way I figured it, by the time I went through the vetting process, a dog was trained and available, my dog will have been fully trained for over a year and helping me the whole time.
I understand few people have the patience and/or option of training their own dog. California, where I live, is very friendly (at least on paper) to service dogs in training making the process easier.
I do wish I had professional help though. It is a lot of hard work, and I'm not making as much progress as if she were being trained by a professional. There are some benefits though of doing self training. One benefit is I'm learning patience and bonding with the dog more than if I just went somewhere and picked up a fully trained dog. One of the hardest things to remember is that she is still just a pup. I can't expect too much from her yet.