There are gennerally 2 types of wells, shallow or deep.
Shallow wells often have the pump up on the ground (aka jet pump), and are a bit cheaper to deal with. However they tend to fail or give problems or less performance a bit more often. These wells can be very small pipe in the ground, or a big 3 foot diameter hole.......
Deep wells typically have the submersable pump which is deep down on the bottom of the 1" pipe, all of which is inside a 5" well casing pipe. These generally are over 100 feet deep, can go deeper than 400 feet. These pumps are real spendy & labor to get to, but are rather dependable & last a long long time, run cooler & push a lot more water.
This is general operation, there can be many variations of course, and some deep well casings are only 4", some are 6" or bigger for irrigation, etc.......
In the future, you can ask what type of well it is, and what type of pump, and how deep the well is. The seller _better_ know these things, or be able to locate well person who does know. In the past few decades many states keep records of these things. You need to ask questions on disclousures like this.
Costs will depend a great deal on which type & how deep the well is.
Me, it would be a big bonus to have a deep well with the pump missing, pay less for the land, put in a good new one with the savings, and know you have a dependable source of water for the next 15-25 years, no fuss no muss. Sure beats paying full price for the land & having to put in a new pump in 2 years when the old one fails.... You might be overlooking the benifits of slight 'defects' of a new property????
--->Paul