Between RX 350 or GX 470 Which one should I choose to get for my mother? What maintenance should I look for if I am getting a used one from 2004-2009? and whats are the differences between a car that had 4 previous owner and a one owner car?

do not buy a 4 owner car, too many IFFS. RX 350 have less maintenance and better gas mileage

Get the RX350. As Scotty said “RX350 have less maintenance and better gas mileage”. Not only that Parts are cheaper and very common to find because the RX350 shares the same engine as the Toyota Camry, Highlander and heck even the Minivan Sienna. With the RX350 you’ll easily find parts.

All parts are interchangeable on those vehicles