Hello and welcome to the LOC.
Good examples are becoming hard to find and those that are are fetching some crazy prices (take a look on ebay for the low mileage examples!)
Is there any particular year you are looking at, the last model (series IV) is considered by many to be the best of the bunch with all of the niggles from previous years ironed out and of course the specification is higher with built in sat nav for example but even this is outdated by modern standards.
The power steering leak is common to the early models and is generally due to the failure of a simple O ring.
IIRC the cambelt is a 60,000/6 years for the non VVTI and 100,000/10 years for the latter VVTI model.
Time for replacement is around 8 hours, Lexus dealers often offer competitive rates on the job so worth riinging around.
Good luck with your search,please feel free to post up links for any you are considering and we will give feedback both good and bad :)