First off, welcome to the board! Thank you for taking the time to come over to join us, and I hope you're able to find a Sonex that fits your mission.
You've asked an excellent question and its one that's been asked before. I encourage you to go to the following:
www.sonexfoundation.com and look on the right where you will find a tab labeled 'Safety & Education.' If you click on that, it will take you to a 'Pre-Purchase Inspection' document that was written along with the Sonex factory in order to offer some guidelines on people puchasing completed airplanes.
At you leisure, please look that over and let us know what additional questions you may have. I think you'll find the Sonex line in general very overbuilt, robust airplanes and fairly easy to inspect.
Again, welcome to the forums, and don't be a stranger! Let us know how we can help you!
Thanks,
Mike