There seem to be so many variations in the way everyone wants to do the singular possessive: apostrophe alone sometimes, apostrophe s sometimes. Does the word end in s? How is it pronounced?
The rule is so simple: Add apostrophe s to the singular form of the word for the singular possessive -- no struggles, no mess, no consternation, no having to decide.
...Mr. Well's car is in the shop.
...I believe Mr. Rogers's address is incorrect on this form.
...We saw Ms. Burns's report on this matter.
Happy punctuating!
Margie