Hi. Welcome.
I look for the amount of wear. See if it looks abused or was well maintained. 1800hrs is not much accept for the fact that the tractor is 40 years old. Check the fluids to see if they are up and look like they have not been in there for 10 years. Listen for knocks, squeals, grinding. Does the owner have service records. Find out why there are so few hours on it. It has averaged 45hrs per year. Check with a dealer on parts availability.
Drive it around and use all the functions. The MF 235 was made for only two years. 1975-6. Cost $6,900 new. Check ebay and or craiglist to see if any are on the market and what they are asking.