I have a Lab/boxer mix that was abandoned at the vet's along with 12 other pups & the mommy dog. We adopted her. Anyhow, when I was unable to walk or reach for things because of my back, Hi-Dee would do it for me.
If I dropped the tv remote & she was in the kitchen or sound asleep, she would come & pick it up for me. When she saw that hubby was taking off my shoes, she would go grab my slippers. At night, she would lay down behind me after I got in bed to act as a support for my back. I wouldn't sell/trade her for anything in the world.
Here in Ohio, the 4-H kids usually have 'pilot' puppies, They train them to sit, speak, alert you when they have to go out to do their business, etc. Myself, I would suggest you check into that kind of program. The pups are about 4 months old when you get them & there isn't a cost to you. (That's what my neighbor told me & her friend's daughter did this for several years. The kids just get heartbroken when the pup goes to a new owner, but they know they were doing a great service to others.)