Check the state of the tyres (whether they have perished or are capable of movement, etc) and the pressures
Brakes
You may also find that brake shoes have adhered to the brake drums, with rust. They may free off if the buses are towed a few yards, or they may remain rusted on, locking the wheels.
Transportation
If an RLH is to be towed on its rear wheels without the engine running for over three miles, the rear propshafts must be disconnected (otherwise the gearbox will not be lubricated and may be damaged). If you are using transporters (low-loaders), watch ground clearance at the rear ends of the buses, they are very vulnerable to damage.
Chassis Corrosion
The chassis (the frame underneath the body) is steel and the main members extend all the way from the front to the back of the bus. These are usually structurally sound, which is good since they will support the body.
Structural Body Corrosion
The RLH body has a steel frame, this means it is rigid and unlikely to fall apart or sag. There are also some Aluminium bits. The steel areas of body frame to watch most for corrosion causing weakness would be:
the riser. This is a transverse beam which actually forms the step from the rear platform into the lower saloon. Severe rust is very common, making it bow outwards.
the fillets at the bottom of the lower deck windows. Inside the lower saloon, level with the window pillars, just under window level there are triangular metal plates riveted to the walls. Check for rust behind them (if present, it will push them outwards creating a bulge).
where the top deck is joined to the bottom deck (only visible with exterior panels removed)
the frame supporting the rear platform around the perimeter
the metalwork supporting the lower deck floorboards, visible from underneath the bus
Exterior Panels
Attached to the body frame are hardwood inserts which in turn are used for screwing the (Aluminium) beading, (Aluminium) exterior panels, and (Steel) window pans. If water has got behind the beading, or through rusted or leaking window pans, then this wood could be rotten which could cause panels to come loose or fall off in transit.
Window Pans
The steel window pans are perhaps the first thing to corrode on an RLH which has not been kept waterproof or stored inside. Also, the window rubbers become cracked and once water starts to enter, things get worse. Poke the window pans from outside the bus, next to the window rubbers, and if the screwdriver goes through they are rotten. Be aware that windows could fall out in transit in extreme cases.