But he seemed pretty sharp, and was even considering selling his personal residence up there because of how overheated/low affordability Marin is getting.

get references from the builder, ask for his last five jobs, talk to those people.Builders can be great sometimes, and bad at other times, it is almost what they can get away with.Don't pay until job is completed, do not pay up front, if the builder can't afford to buy material to start the job, you need to find a more secure builder.

The question is, can you afford to lose the condo.

Parks offer a very affordable option at a great value and you can't build new ones.  

I clearly stated in the letter that we(my wife and i) are interested in the property, but would need owner financing for a couple of years before we could afford to refi and pay him off in full.

Let them stay at an affordable rate and count your blessings.

Most of the families (hardworking, middle class) that we showed the apartment to were people who simply couldn't afford Dover prices anymore. 

@Xavier Jefferson some people can't afford a down-payment on a house and rent a SFH is the next best thing.

Also, great post on the Blog - The Creative Way to Gauge Whether You Can Afford Your Rental's Worst Case Scenario!

Put it differently, the multi-million dollar homes are not selling and more affordable lower million dollar homes are selling well.