If you are only looking at a Ford Explorer, I wish you luck. It is not one of the reliable cars at Ford, getting bad reviews on Consumer Reports and on TrueDelta. TrueDelta says its average reliablity is at 171% - or well over average for the number of issues it has (2011 on).
It is only slightly better in 2016 and 2017 at 149% for average repair frequency.
Going to Consumer Reports, it gets the red circle of double arrow down for overall reliablity in 2012 and 2016, one arrrow down overall for 2011 and 2013, average overall for 2014 and 2015, and slightly above average in 2017 because the car is too young to have issues yet.
If you are bent on getting this car no matter what the slightly better years are 2014 and 2015, where you only have to deal with issues on the climate system, suspension, brakes, exhaust, paint and trim, body integrity, power equipment and in car electronics.
Want something more reliable? Consider the Toyota Highlander where you only have to avoid the 2014 model year which has some real problems with the electrical system as the other years from 2011 on are pretty good. Even the Chevy Travese is better as it shows up as average in Consumer Reports for most years from 2013 on, and above average reliablity for 2016. Toyota is the best in this size of class however.