Hey Kosmo, back on your question, I had a
L4150 for a few years. That price seems high, especially with high time on it. It was a great product when new, but a lot can happen in 3400 hours.
The
L4150 is a very good tractor - big bones, great build quality, smooth 5-cylinder engine. The hydraulic shuttle was harsh above idle (re-valved in later years on newer models
L4850 and
L5450)
In those years I think the two backhoe choices were a Kubota-branded 9-ft and a Bradco 11-ft. Both had subframes.
Look it all over - if zero leaks anywhere that's a good sign. Start it up stone cold, watching the color at the stack. Any blue should clear right away. Listen for knocks or ticks. At normal idle rpm, loader and backhoe should lift the machine without effort. Steering should be smooth and easy, with no wobbling joints. Loader and BH joints should be tight. Shuttle should be smooth and silent.
One fact about Kubota tractors made through the '80s is they hold their value - often selling for nearly the same number of dollars as they age. But even the best tractors, backhoes and loaders get worn in 3400 hours - with the high hours everything else on this one would have to be pretty sweet to still be worth $20k.
If you post some pictures of it they can tell a lot about the life its had. Best luck. Dick B