Maybe First Hill is special, but parking in Seattle proper and Capitol Hill (both near First Hill) is extremely crowded and finding a spot can be hard. The mythical building plot described in the article sounds wonderful relative to my experience:

"Overnight, when your tenants’ cars will most likely be at home, the office buildings’ garages are usually empty. And, of course, there are hundreds of curb spaces within six blocks of your building, though neighbors’ vehement territoriality about “their” spaces would make it impolitic to mention those in an appeal to the city for a parking waiver. Odds are that your tenants could secure whatever parking they wanted for much less than $250 a month per spot."

The cheapest parking I could get on Cap Hill was $150/mo, and it was in one of these subterranean garages.

Speaking of garages, any reason you can't build the garage on levels 1-2 and put apartments on 3-5?