I have had an 2003 LS V-8 Sport and then went to Jaguars. Still love that 2003 LS! I have worked extensively on several XJ's of that vintage. They are very good cars but have their problem area's like all cars. Not much was shared outside the drive train.
Be aware it was Jaguar's most expensive car and that is reflected in ALL the repairs. The great thing about Jaguar is yes they are expensive but they keep parts available so you actually can fix the cars!
You want the latest year possible much like the LS as many running changes/improvements were made over the years even though the cars looked about the same. The 4.2L engine and the 6 speed ZF transmission are rock solid and will last many a mile! Please change the transmission fluid as ZF at least in the beginning also had the filled for life crap posted. Same as the Ford transmission in the LS there is no dipstick and a pain to check fluid levels.
The engine has the third version of the timing tensioners and are not a problem. But stay away from the Jaguar 4.0L V-8 as it's the same as the first gen LS and you will need to replace the tensioners and chains or risk destroying the engine.
Now your picture shows the weak spot of that car!
Note the red circles. That car still has the factory 4 wheel air suspension. It is troublesome and failure prone especially at this late date. So much so that the recommendation is to replace it with springs. There is a kit out that makes that swap easy and includes a special electronic module to shutoff the dashboard trouble lights you will get if you just disconnect everything.
The air compressor and front struts are the first things to go. You can struggle and replace those but it's all very expensive and will probably give you more trouble later on. The good thing is you can't tell much difference between the air suspension and the springs unless you drive them back to back. The air is smoother and springs really can't compare but almost every other car on the road uses springs so we are all use to how those feel.
Finally and this is why I went to Jaguar. They are worth nothing so really bargain when buying one. They can't give them away because of the old Jaguar unreliability reputation. Also only get it if you can DIY the repairs again because of cost at the dealer. We have a very active forum and all the problems have long been solved.
That car looks clean but the XJ is all Aluminum so it won't rust but salt can still cause corrosion so take a look underneath. From the engine compartment picture that one looks like it's from a non-salt area?
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