Support them emotionally. There’s nothing that deflates an entrepreneur more than winning and having no one to share it with. Winning is almost as stressful as it is when things don’t go as well as planned. In both instances, your friend may need a shoulder to lean on. When they win, there is pressure to win again, and they may need you to tell them they can do it.
When things don’t go as well as they hoped, they need you to tell them to keep at it and that you believe in their talents and abilities.