Originally Posted by
Dudelsack
Standard n00b fare: ride a little at a time until your tissues toughen up. Don't worry about distance and speed for now. Don't expect to be a ball of fire for 2-3 years. When you want to get faster, ride with a club. Read a lot, dismiss about two thirds of it. Ignore all posts about average speed. Buy a new bike whenever you want to if you can afford it. If it doesn't work out, list it on Craigslist and make someone else very happy.
I think that's it.
What he said. Plus....I'd get a trainer or rollers (if you can manage them at some point) and read about cycling diet and exercise for people over age 50. I'd start with "Younger Next Year" and then move on to something more cycling specific like "Cycling Past Fifty."