Its not the breed that you're going to have problems with, its the fact that is was a puppy mill dog. I've always heard good things about Basenji's, they are smart but energetic, so a lot of activity will help.
Give him lots of love and time. He will be scared and unsocialized. Talk to rescue groups and other people who have experience with puppy mill rescues for training tips.
Good luck and god bless you!!