I have a friend who had to put her doxie/border collie to sleep last fall. Tilly was 16 at the time and had serious kidney disease and M really, really went the extra mile to help Tilly be comfortable for as long as possible. M still has a 6-7 year old sheltie mix at home, no kids, has a long time partner.
M is looking for a puppy herding mix of some kind that isn't too crazy, but would be interested in having fun in flyball and/or agility. The dog doesn't need to be a high caliber competition dog, just one that likes to have fun. The sheltie has luxating patellas and can't do either sport anymore, even after having surgery. She's only ever had females and that's what she's looking at this time around - she has a garden and prefers dead spots on the lawn to legs lifted on the flowers.
M would take the puppy to classes and in my opinion is the type of owner pretty much any dog would be lucky to have. She and I have done a bit of a Petfinder search, but nothing has really jumped out so far. She's in no hurry, just ready to let the right dog pop up when it does.
M lives by me in Madison, WI but would probably be willing to head as far south as St. Louis.