20 years ago, we had a Deere, 41 hp that had serious mainetnance problems when it had to pull the 5.5 m3 manure tanker.
Later, the 45 hp
Zetor 4712 pulled a 6 m3 manure tanker with the 3 meter cultivator in tandem (direct manure injection)
This baby only had some clutch trouble because after 26 years, some clutch fingers broke.
The 6718 is the same type of tractor, just keeps going and all we did is replacing a ring in the tranny that held the tooth ring of the tooth clutch engaging the fifth gear. (the
fuel tank rubber were broken and caused the fuel tank to hang against the gear lever, what caused this problem)
Our current 5245 is not as good, it is abused (driven without any cooling water when the water pump broke) so the engine consumes too much oil. I have replaced the weak spots of it, the clutch and brake master cylinders, the water pump and the gear lever got a factory modification (under warranty) when we bought it.
If you want a cheaper one, you should be looking at a 7 series. The newer 0 and 2 series are all too expensive second hand, they are very popular export tractors to the east, and Baltic states. The 7 series was trouble free, the later 2 series had some problems but the replacement for the weak components are improved and trouble free.