I'm new to dogs and feel so ignorant sometimes

. I'm reading a basic - cover all the topics related to puppies - type of book. It suggested that I always use the same door to take Max out to use the bathroom. That makes sense - except for the fact that we have 2 levels with doors and we spend about equal amounts of time on each level. If we're in the basement - it sure would be quicker to make an exit out the sliding door down here for his potty trips. He's already had 1 accident because we couldn't get up the stairs to the front door in time. I generally take him out every 1 - 2 hours and after meals.
Has anyone else house trained and used 2 doors on 2 different levels? If so, were there any problems related to that?
Thanks!
Eilene