White stripes down the page
This is usually the corona wire, and cleaning it takes ten seconds. Open the front, pull out the drum and toner assembly, and find the green tab on top. Slide it from one end to the other and back, several times, then park it in the home position in the middle. If you leave it off-centre you'll get a stripe in a new place. Print a test page. If the stripes survive that, the drum unit is the next suspect.