What's the minimum Renegade/Paragon points you must get?

Follow-on to this one: Can I play Mass Effect 2 with 0 Paragon points?

While it's impossible to play a character 100% Renegade or 100% Paragon, surely we can try. To that end, what is the least amount of undesired reputation that can be gathered? I'd like answers for the following:

• Attempting to play pure Paragon, avoiding Renegade whenever possible, how much Renegade points are unavoidable?
• Attempting to play pure Renegade, avoiding Paragon whenever possible, how much Paragon points are unavoidable?
• Attempting to play a completely neutral character, avoiding both Renegade and Paragon points, how much of each are unavoidable? (Is such a character even possible, or practical?)