Older dogs CAN be trained to do whatever a puppy can be trained for. If they aren't housetrained, they can be trained quicker because they already have control. And older dogs seem to realize that you are their saviour. They can also try your patience, testing to see if you really will keep them. It all depends on what they've been through.

I think in your case, a young and submissive dog would be better than a puppy. Jmo.