**UPDATE
Good lord, I had no idea this garnered so many responses! All of my notification emails were sent to my spam folder. So before I respond, let me just say thank you to everyone that posted a response for me -- it is greatly appreciated it.
This is what has happened since I last posted...
I had my agent (not the seller's agent, but my own) do some leg work and speak with the city, and include me in calls and communication with the permitting office to find out what it would take and what it would cost for me to bring it up to code since the seller is unwilling to (and, honestly, with a line of people wanting to buy the property, why would he? It's unethical, but what can ya do).
Every person I spoke to said the patio was not really a big deal since it was less than 30" off the ground, but the cover would need to be permitted. The strange part is every one of the people I spoke to with the city said it was incredibly unlikely that anyone would "find out" unless someone called it in because they don't go seeking out homes with work that isn't permitted. They just don't.
The cost to get it permitted is not as costly as I anticipated and would likely be around $1500-2000 for ATF permitting fees and architectural drawings and inspections. Luckily, I'm friends with a civil engineer and architect who has offered his services for providing drawings (necessary for permitting) and making adjustments as necessary to bring it up to code, if it isn't up to code already.
During my inspection of the property, I had a contractor look at the structure to make sure it was sound, and I was given the go ahead as far as stability and construction is concerned. He could not speak to current codes, but I was told there was no issue as far as the patio collapsing and, at minimum, setbacks and lot coverage compliance was upheld.
Additionally, all other work was performed with permits (new roofing, HVAC, upgraded electrical, etc.) and the house is otherwise in pristine condition, which is rare for the area, type and price of the house. This damn patio is really the only thing keeping this from being a near-perfect property.
After deliberating and weighing the outcome of each scenario, I decided I would move forward with the contingency for the seller to escrow funds to take care of the ATF permitting. I want the house, but I ain't gonna let the seller get away without at least contributing heftily to the permitting of the porch
If it turns out I have to tear the porch down and rebuild, it'll be a headache and a little bit of a heartbreak, but I am also prepared for that if need be.
Thanks again everyone for your input, you helped me move forward with fully opened eyes.