this isnt my car, its a cavalier of my friends
the car would start for a week but was hard to turn over
now when he turns the key it just clicks

his lights and car works, what could the issue be... it wont turn over just clicks...

Low battery voltage. Get it tested.

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starter could be bad as well

Actually charging the battery overnite,then take the starter off and get it bench tested at auto zone or advance auto for free.Sounds like either can cause this,I would lean towards the starter if the battery once charged is solid,and try starting if it drags,hesistates to start the starter prolly is the issue.Bench testing is pretty good but,does not always show failure(if there is a dead spot) on the starters solenoid.