If I have good credit, will letting someone with bad credit add me to their account bring down my score?

Question by Joshua P: If I have good credit, will letting someone with bad credit add me to their account bring down my score?
You might ask why I'd want to do this...well I have great credit right now but not enough tradelines (meaning its new credit and I dont have sufficient credit history to qualify for a good mortgage rate). I was approved for 100% financing under the condition that I have sufficient trade lines. So I'm thinking of having my dad add me as an authorized user on his cards

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