I've just read John Molvar's Lydiard workout program, where he claims that "you can and should take a sedentary office worker who has never done anything physical his whole life and get him up to 100 miles per week in 9 weeks":
http://www.bunnhill.com/BobHodge/Special/LydiardInterpreted.htm
I'm going to try and do this, but in a milder way. Instead of building up to 100 miles a week, I'm going to build up to just 100 km/week. I'll be following the schedule in his table to keep it accurate (3 km the first week, 11 km the second week, 22 km the third week, etc). I haven't run in several months since retiring from competitive running last track season, so this will test Molvar's thesis. If I get injured during this milder buildup, then we can say for sure that you can't take a sedentary guy and build him up to 100 MPW in 9 weeks.
Any guesses on how this will turn out? I didn't gain much weight since my last track race, and I still played some sports 2-3 times a week to keep in reasonable shape.