Each example you come across is likely to be a completely different situation. Some may go a long time without needing anything. Some might fall apart around you. With some very careful inspection and patience, you should be able to find a good one. Try to find out as much as possible about its history and maintenance. I always prefer the completely unmodified examples. Modded trucks often led rougher lives and the aftermarket parts usually aren't as reliable.
I love the 1st-gen 4runner (1984-1989)...I've had the '85 for 15 years and plan on many more. The 22R-E, 2.4L I-4 has a great reputation for longevity and is easy to work on, and the rest of the drive train is stout. The 1st gen is the 2-door body style, very similar to the Truck. It has a removable, fiberglass hard top. 1984-1985s had the solid front axle. 1986 and newer has independent front suspension (IFS). Fuel injection was standard from 1985 and newer. 3VZ-E 3.0L V6 option added in 1988.
I do love the styling of the 2nd-gen 4runner (1990-1995). It was the first, all-steel-bodied 4runner available with 4-doors. Probably my biggest gripe with them is the power back window--it can be temperamental, and it needs to work in order to open the back tailgate. The 1st gen has the power back window as well but you can get around using it by switching to a soft top. The 3VZ-E 3.0L V6 has a polarizing reputation. It did have some head gasket trouble when it was new but the issues have pretty well been resolved by replacement under the technical service bulletin, which all of them should have had by now. It's not as potent a V6 as the newer ones, but it does have a chunk more output than the 22R-E and runs smoothly, if in good repair. Those who have them usually like them. The 4-speed automatic is not very power efficient. The 5-speed manual leaves you with more usable power. Unfortunately, most of the 2nd-gens have the automatic.
The 3rd-gen 4runner (1996-2002) had some key improvements. It has more powerful engines including the very satisfying 3.4L 5VZ-FE V6 and the 16v 2.7L 3R-Z I-4, which had almost identical power output to the earlier 3.0 V6. The third gen got a rear lift gate that replaced the tailgate, a roomier rear seat with better access and additional options such as the available, electric rear differential locker. Towing capacity with the V6 is increased to 5,000 lbs. Automatic-transmission examples can experience leaking trans coolers, leading to "pink milkshake" issue with engine coolant. High-mile examples should have lower ball joints replaced...some have been failing.
I prefer the 4runners to the Land Cruisers for general exploring--they're lighter, more fuel efficient and usually easier to own.
In the Land Cruiser arena, you'll probably encounter the FJ-60, FJ-62, FJ-80, FZJ-80 and FJ-100 (depending on how new you go).
FJ-60 (1980-1988): Utilitarian, large 4-door wagon with large-displacement, carbureted inline-6. 4-speed manual trans common.
FJ-62 (1988-1990): Same body as FJ-60, but fuel injection added and manual transmission dropped. Minor interior refinements.
FJ-80 (1990-1991): New, more rounded body style, full-time 4wd
FZJ-80 (1993-1997): Same body as the FJ-80, but with more powerful 1FZ-FE 4.5L inline-6. Towing capacity increased.
FJ-100 (1998-2007): New, larger body style. Lexus-derived 4.7L 2UZ-FE V8 replaces inline-6s. Independent front suspension replaces solid front axle.
There are also other variants you might find--research them as you encounter them if you're interested.