Duck,
Don't even think about a C-172 unless the SID has been completed, and still have an independent LAME do a very thorough pre-buy --- it will be the best $1000 or so you ever spent -- particularly if it means walking away from a well presented dog --- there are plenty about.
There may be no SID for Piper, that doesn't mean they don't corrode and crack, again a very thorough pre-buy is essential.
Of course it may not mean walking away, even with work to do, if you astutely use the pre-buy report to negotiated.
On any pre-buy, if you don't find corrosion, you haven't looked hard enough.
As an example, I have seen a asking price of $52,000 for a quite presentable PA28-180 bargained down to $38,000 because of what was found during the pre-buy.
Tootle pip!!