How many sources do you check before you feel confident that you understand something? What if they all disagree? What then?

I don't check any "sources" - I have a life, a job, a husband, interests, activities, friends, which are more important to me than any academic "checking" of "sources".  That is for people who love doing that kind of thing. They can write term papers and dissertations and collect degrees.  I have different interests.  Anyway of course people are going to disagree because no two people are alike.  We are all different and have different needs and outlooks and beliefs etc. so I just have to trod my own path based on who I am.