PA-28 pilot reported not knowing aircraft was not properly repaired per Piper specifications when flown.

Narrative

I was intending to purchase Aircraft X for a leaseback to a local flight school in ZZZ. To initiate the Pre-Purchase Inspection and Annual; the flying club and myself entered into a contract with prearranged insurance coverage and approval from the flying club provider. Before takeoff; I ensured all logbooks were with the aircraft as well as all documentation was aboard the aircraft to ensure a legal airplane. During my logbook inspection; Aircraft X was legal to fly until the end of the month before the annual needed to be conducted. The annual was arranged to occur on Day 0. During the start of the Pre Purchase Inspection-External Observations; I was contacted by the A&P to stop by and look at the concerns of corrosion and additional issues that were found after I flew the airplane from ZZZ1 to ZZZ. The initial findings before the annual begun were discovered but not limited to:-observation of several cracks (1-2 inches) in the wing skins on both wings that were stop drilled to prevent additional growth. Per Piper-This is NOT an acceptable form of repair. The service bulletin from Piper clearly states the wing skin MUST be patched/replaced.-lots of surface corrosion throughout the aircraft including the aft wing attach pointsThe A&P and myself called the president of the flight school to discuss these issues. At the end of our discussion about our findings; I notified the flight school that I was not longer interested in the airplane. The flight school was advised that our interpretation of the SBs/ADs; the aircraft is NOT legal to fly until all ADs/SBs are complied with as well as proper repairs and they will need to find someone to pick up the airplane to return to ZZZ1. I am writing this report because I did technically fly an aircraft that is not airworthy (due to improper repairs that were discovered after I landed at ZZZ) after the A&P and I myself did additional research on the Service Bulletins and ADs. In the logbooks; it clearly shows all of these SBs/ADs were complied with. I trusted the A&P did his due diligence to ensure the work was satisfactory with the current ADs/SBs. Going forward; I will do extensive investigating to ensure this does not happen to me again.In good faith; I wanted to report this event so it was in writing just in case if anything additional did happen to the aircraft in question; Aircraft X.