Relatively fit, I'd say a college male could run about a 6 minute mile, this isn't your average kid, this is a guy who did a a sport or two in high school, stays relatively fit, by either doing some innermurals, playing some hoops or football with his friends or even running a little bit.
I'd say if you took the average RELATIVELY FIT college male gave him 5 months under a solid coach, and stays healthy he could do alright by a normal persons standards.
5 months is 21 and 2/3 weeks.
So this guys does 20-30 miles for 4 weeks, 30-40 for the next 4, 40-50 for the next 4, 12 weeks down. Stays about there and starts increasing the intensity with about 8 weeks to go. And is able to bring that mile pr from 6 flat to 5:20-6:00 flat range and that gives him a little bit of speed.
So, if you were able to get a guy that is relatively fit, not some alcoholic that thinks beer pong is a physically demanding activity, he'd be able to run about 30-32 minutes after 5 months.