Cambelt 10 years or 100,000 miles, although its a non interferance engine but good to get piece of mind and saves on recovery costs if it was to let go and water pump replacement at the same time. It should of been done at this mileage but always check the invoice, budget around £400 - non Lexus dealer.
Check everything works, load and eject cd's a dozen times during the test drive - error 4 could help you knock a few hundred off the price.
Drop and raise the suspension a few times, look underneath for rust, little torch and beedy eyes around the engine including power steering pump and all pipes, leaks are common. Just do the normal checks with wishbones, brakes, even tyre wearing, inside and out. Check all the windows and roof, if the one touch isnt working then it needs a reset. Check power boot works.
If it has faults then price it accordingly, plently out there and they are a hard sell with the horrible MPG figures so its a buyers market.
I picked up a 53 reg SEL with 47,000 miles last year for less than £6,000 so you can pick up a decent Gen2 for £4K. I was watching a number of RX's for a month on Ebay/Autotrader before I bought the current one, you will see the same ones advertised for weeks on end - so I looked at the newly listed adverts, the good/cheap ones dont tend to hang around for long.
Good luck, you will be waffing along nicely once you pick up the right RX.