Wrong: I want to retire to a place WHERE I can relax AND I pay low taxes.
Correct Idiom is X and Y .
X & Y needs to be parallel.
in this wrong sentence:
X =I want to retire to a place WHERE I can relax
AND
Y = I want to retire to a place I pay low taxes.
X & Y are not parallel because WHERE is missing in the Y.
you can say that we can take "where" as common word ( so called ellipses). you may be right in other cases but not in this case. you can get judgement from the meaning of the sentence. in this case absence of WHERE in Y making this sentence not clear in its intended meaning.
i hope that would be helpful.