A used Lexus needs to be bought with care and due diligence.
Merely buying it because it is a Lexus is somewhat short sighted in my view.
If buying from a Trader then, as with all cars checking that a full (preferably Lexus) service history and all/any recalls have been carried out are both essential. The Trader is then required by Statute to remedy any significant faults occurring within 6 months of purchase.
If buying privately, then check the service history and condition . If all services have been demonstrated and the condition is acceptable, then enter into a contract with the seller, so that in the event of clear misrepresentation the buyer can seek redress via the courts.
If an acceptable service history is not demonstrated or the condition causes concern , then unless you are knowlegeable and competent re cars and their requirements, walk away.
Do not fall into the trap of thinking that because it is a Lexus you will not have any problems.