The key factor is this guy wanted a fixer upper and committed to doing some rehab himself, is qualified to do so, perhaps an unusual combination of circumstances?

An ideal situation would be like a paid off home that was passed down to a family member, and that person neglected the taxes for a few years and was at risk of losing the home.

And frankly, there are some much more expensive homes in this established and attractive neighborhood.I wouldn't, under normal circumstances, consider selling it at this time because homes in this area are appreciating pretty rapidly and I'm the kind of guy who would prefer to milk this for as much as I can get of it. 

. ;-) But I might under the right circumstances.

Sorry everyone, I became really busy with work the last couple of weeks and neglected the forum.  

I often use addendums to permit pets and other circumstances as well.   

----------As Anthony G. and Ellis San Jose point out: it depends on one's personal circumstances, resources, a good team, time, skill set, risk tolerance, & resources.

I started to suspect their inflexibility was due to a change in their circumstances and a desire to stay in their home and this was confirmed.  

That would have given him time to stay, except in very specific circumstances.  

That way, in the near or distant future, if circumstances change, they'll come back to you.