They are generally very good, check a few things like- rubber hoses attached to the turbo that are prone to splitting, clunks from the rear axle when driving as this can be the rear diff mounts on the way out. The TD4 is quite economical and generally very reliable (BMW engine) check for oil leaks and clogged up air filters. Check for corrosion behind the spare wheel on the door and check the rear window operates correctly too, this should drop as you open it an inch or so to allow the door to open

The M47 engine is generally reliable, it likes good filters and quality oils. You can get Genuine LR service kits on ebay for under £100.

The EGR valve clogs up, £45 to blank, easy job to do.
The hoses split with age and oil contamination, you can get replacement silicone ones for about £120.
Removing the crankcase filter for the modified BMW vortex filter, about £40.

Auto's are better for off road and towing, but do 3-4 mpg less, and some of the 55-06 ones fall into the £460 road tax bracket. Change the oil in it every 60k for a good box life.
Manuals are decent, but can suffer from master/slave cylinder problems. If it's the master then it's about £137 part and then labour. Slave cylinders are a gearbox out job and a new clutch/flywheel for peace of mind.

Make sure it has the VCU and props fitted. If they are missing, it's cause the VCU is fecked, don't buy bullst about it being in 2wd for fuel economy, it makes little difference in real life.
Prop bearings can grumble, £40 from foundry 4x4 for proper GKN ones,

Otherwise, just check the electric's all work and that the boot doesnt leak.

Buy SE or HSE spec for best toys.