You have the right attitude, dont buy on impulse. Its tricky when you hear the exhaust and take a test drive but keep a level head.
Prime example my first zed was a roadster, it was in great condition but i noticed some issues with the roof. Garage said np we will fix it all so i agreed and bought it. I absolutely loved the car and don't regret it but with hindsight i should have waited and picked a better one. Those roof issues kept resurfacing and it occasionally leaked when it rained -not fun. Eventually it started ruining the fun so i sold it and moved to a 370. Waited for the right one and never looked back.
Funny thing is i look back very fondly On that first zed, despite the leak i loved that car