If your neighbour is looking for a rescue Cocker, it's extremely unlikely they will find one that has been health screened for the various hereditary problems that crop up now and again. A rescue dog will probably have received a basic veterinary check up but nothing more. If you want to know more about health issues in Cockers, have a look at
http://www.thecockerspanielclub.co.uk/health.htm. If your neighbour was considering a puppy from a breeder, they should be looking for parents of a litter to have been annually eye tested, DNA tested for prcd_PRA, DNA tested for FN (hereditary kidney disease which thankfully is quite rare) and possibly hip scored too.