It’s not so clear cut. There is evidence that shows impact sports like running increase bone density, which is very important down the road.
Although if you start running, you will hear this “advice” from a lot of people, I’ll just warn you right now.
I posted this concept in a bike thread and I’ll post it here.
If $100 shoes gets you out and running, go with $100 shoes. If the cost of expensive shoes keeps you from running, get cheaper shoes and run in those. The important thing here is to just get started. Just be sure to start slow. The couch to 5k program looks really good so I’d recommend going with that. With a program like that you really won’t need expensive shoes.
In the end, you are a single experiment. Find what works for you. There will be no shortage of people with anecdotal testimony about how certain shoes/socks/shorts/hydration/nutrition/sleep/time of day/technique/surface/partner/cross training/stretching/etc. cleared up all their running woes. Listen to them, try their advice if you must, but find what is best for you.
My experience has been the same as TroutMan’s: when I started running 20 years ago, I was a heel-striker. Had major shin splints. Almost gave up running entirely. But then someone told me to try landing on the ball of my foot, when my foot was directly below my body, and then to “push off”. This changed everything; my pains went away, and I ran more efficiently.
As for shoes, the best advice I can give is to start with a pair mid-priced running shoes. If they work for you, try a cheaper shoe. If they don’t work for you, try a diffrent or more expensive shoe.
I walk corrected. :smack:
Six years ago, I did the C25K – I weighed about 275-280 pounds at the time. I did have decent shoes, but since I don’t have foot issues like pronation, I never went to be “examined” by a running shoe store. It’s a pretty easy, gentle program, and I liked the discipline. It felt good to be running (albeit slowly) for 30 minutes as I neared the end of the regimen.
Now I just walk, to study music or maybe a language tape, but I run up the hills without fail.
If you know that’s the case (and it sounds like you did), and it works for you, excellent. For someone who’s just starting out, like the OP, it may be worth his while to seek out a fitting, since he may not know what his stride is, and what sort of shoe may be best for him.
I took up running two years ago at age 46. This spring I ran the Boston Marathon. I think starting running so late in life was my strategic way of avoiding any knee damage. 
Take it slowly, listen to your body, and find some other experienced runners to go with. You’ll get some advice about your stride, helpful hints, and encouragement.
I also recommend going to a running store and buy at least one pair of shoes there. You can probably start slowly on the C25K program with cheaper shoes but I really believe that having someone observe your stride and direct you to a good pair of shoes would help immensely in the long run. (pardon the pun)
Stretch after running, not before.
If you’ve been sedentary, or not doing anything much with your thigh muscles (quads), consider strengthening them for a few days or a week or so before running (by stair-stepping, for instance); it’ll save you a lot of hobbling around in pain.
Do you say this in the sense that “If you can only do before or after, choose after,” or are you advocating against pre-run stretching no matter what?
I wake up tighter than a drum most days, and if I don’t stretch before my run it’s generally pretty miserable. I’ve been led to understand that the post-run stretch is critical, as well, so I do that - but its effects are not as immediately obvious.
Stretching when cold and tight is a good way to pull something. Muscles are more pliable and responsive to stretching when warm.
Try walking into your run to warm up rather than stretching before. You might even find you’re not as tight in the morning.