I'm glad David brought up the issue of boats, because they are the cause of my biggest concern about A/C ownership. How many boats do you see parked down the side of a house, going nowhere? Too many, I reckon. I used to live behind a bloke with a boat, and every weekend he'd turn the motor over to keep it in good nick, but in the years that we lived there, that boat never got near any water. $50k might seem like a good idea while we're all enthusiastic, but will it fade over time and leave you with a very expensive paperweight (and yes, you could sell, but have you noticed how many a/c are for sale each month in the RAA mag?).
Having said all that, I love building things, so the retirement plan definitely includes a little(?) bit of a/c construction. All I have to hope is that the money holds out that long.