I ended up buying the 02 nissan altima for 5000.00 with 105,000 miles

Does it sound like shock absorber mounts? I have seen the ball and socket sway bar links wear and cause a rattle going over bumps or rough roads on some cars. Could it be the exhaust contacting the chassis somewhere? Check the exhaust mounts and check for exhaust damage and correct routing. Could it be a loose trim or bumper, check all hardware and securing clips are in place.