Adopting an older dog not only gives him a second change but may also be better for you. Puppies are cute but require a lot of time and effort with toilet training, general training (learning manners!) and cannot be left alone except for very short periods of time. Young adults may need a lot of exercise and mental stimulation or become very destructive. An older dog is likely to have manners already and also to need less vigorous exercise. He may also be comfortable with being left for a few hours (Not the whole day! No dog, whatever his age, should be left alone a full working day!).
There are downsides and we need to be realistic. An older dog may have bad habits or come with ’emotional’ baggage due to a previously unhappy life. However, most dogs are put up of adoption not because they need to be rescued from abuse but because their owners’ circumstances change through divorce, job loss, change of accommodation or new baby (YOU DO NOT NEED TO RE-HOME YOUR DOG IF YOU HAVE A BABY – BUT THAT IS ANOTHER STORY!)
An older dog may also health issues, and may be too old to be insured. However, any dog requires considerable financial commitment over his lifetime and puppies can come with health issues or develop long term conditions which may not be covered by or run out of insurance cover. An older dog may be a little grey around the gills but is likely to have reasonable health to have reached old age!
If you would like an older dog of a specific breed, most breeds have one or more Re-home/Rescue association. The Kennel Club keeps a list of contacts. You may have to wait a while for a suitable dog, especially if there is a lot of demand for your chosen breed. Think of it as a pregnancy: worth the wait in the end!