I bought my N20 w/o sailing, but I knew the following:

1) I liked the N20, having crewed on one
2) I needed a N20 to do Tybee
3) The boat I was buying was FAST, as in FASTER than FAST. It had placed top 3 in nationals on numerous occasions. This was also immediately apparent when we used the previous owners stock settings, old sails and beat 4 other very experienced N20's upwind for 10 miles the 2nd time out on the boat.

In short, it really depends on what you are buying. If you are picking up a $15K racing boat from a guy who is a top level racer, well, you expect that all the bits are there and he will provide some level of support after selling the boat in the form of tuning and getting up to speed. If you are buying a $2k H16, yeah, I would be checking that thing to make sure all the parts are there!