I think it depends on the boy. I adopted Jordy from rescue when he was 1.5 years old and he had been used for breeding. He NEVER humps anything, but he does occasionally hike his leg indoors (mostly when it's bad weather out). Belly bands are great if he does want to hike or mark, and because Jordy was still so young I think it really helped train him, too. I think you should go meet the boy and learn a little more about him, and don't let these issues stand in the way - they can be fixed and he can be re-trained if needed.
I'm so excited for you!! I can't wait to hear whether you get him. Good luck!!
__________________
He is your friend, your partner, your defender, your dog. You are his life, his love, his leader. He will be yours, faithful and true, to the last beat of his heart. You owe it to him to be worthy of such devotion. -- Author Unknown