David - I really appreciate you getting back with me and for your insights. I certainly didn't mean to come across like I was bragging in the above post; the DC area is honestly so expensive that $500k doesn't buy you all that much house in too many places. This home is nice, for sure, but it's definitely a somewhat dated, 1977 split-level that would be extremely pedestrian in most markets. When we moved to this area a few years ago, we looked at a 10-year-old townhome a few miles away that was $200 more a month than we're currently paying. Sat right on a major 6 lane road, tons of traffic, no yard to speak of, etc. People will literally pay more to take care of less (newer, more "luxurious").
We would definitely be buying this home to live in - what did you mean by "house hack a multi-family property"? We have considered the possibility of revenue generation through renting the home on AirBnB during a particular week of the year that draws tons of people and rentals go through the roof. Apparently, we could get something like $500+/night for the home for that week. And there's always the possibility of renting out the downstairs bedroom to a trusted individual but that's probably down the road for us because of our stage of life.
The 3-5% FMV discount is normally super attractive but I'm worried that because of the incredibly high property values right now, we may be in for a correction in the next few years, wiping that discount out (at least in the short run). Part of me wonders if it would be better to rent the property another year, see what the market does, and then approach the owner again. He has made it clear that he isn't planning on selling it out from under us and we can rent as long as we'd like, though he is motivated to sell to us as soon as possible because he's moving into a new home well outside of this area and won't be having reason to regularly come back here to check on it, etc.