Yes, I had one, but she got incontinence at age 7 and I had to give her away. I trained her myself, however, so I did not have to pay for her at all, just had to pay the usual food and vet bills. After they reach about 7, you have higher vet bills and I am on disability too, so I figured that was about the right time to part company with her anyway.
I got the state of North Carolina to certify her for me, which was helpful in the few instances that I needed to prove she was a Service Dog. One doctor's office required it and a store required it one time, but the local restaurants were usually good about it, except one, but when I showed them the cert, they were OK with it then. MacDonald's was the best, though. They had no problem with it what so ever.
Some folks do want to pet them, and they will come up close to you, so be sure to have her red or blue vest on at all times when you go out with her. This prevents them, as they recognize that she is a Service Dog and leave you alone. I learned this the hard way! Even though the owners of the grocery store were cool with her, sometimes folks would want to pet her, unless I had her vest on, then they left us alone. The only exception to this is young children, who may not yet know the significance of the vest. They will sometimes come close and if their mother is not aware of your being there, they may try to pet her. I had this happen once, and I yelled at them not to pet her anyway, pulling her away from them. The stupid mother was offended at me for yelling at her kids, but I didn't care. I made my point.
When I moved to a new town and joined a church she was the most helpful of all though. Folks were pleasant, kept their distance, and she gave me the confidence to meet some new friends and get to know people. The pastor was very nice about it all, even telling the next incoming pastor about her before she arrived, so that when she did arrive, she was very pleasant and knew to expect to find a dog among the congregation.
If you choose to find and train your own, there is a book called HOW TO TRAIN YOUR PSYCHIACTRIC SERVICE DOG or words to that effect. I believe it is by a Jane Miller. My memory is not great, so I might not have that straight, but it is close. I ordered this book through amazon.com.
Good luck and may the Lord be with you, if you choose to go this way.