Please share your thoughts about what is important for 50+ returning or beginning bicyclists.
Here are mine:
Some thoughts from someone who started bicycling "seriously" 10 years ago at age 58:
You will progress much more quickly than you think you will. A 15 mile ride may seem impossible right now. It won't be too long before you whack off 15 miles as a warm-up.
It's more about the motor than the bike. You can start to get in shape on almost any decent bike that "fits" you, and waiting a bit to spend lots of money on a new bike is beneficial, as your thoughts about what kind of riding you want to do most of the time will change, as will your thoughts about "bike fit" and other issues.
Don't be surprised if you find yourself going through a cycle you never suspected. 1st, you may think of a "comfort bike and short rides around the neighborhood." But then you will hear about "hybrids" or "mountain bikes" and you might start thinking about longer and different rides. All of a sudden you may discover a road bike and think about a metric century, or riding your age. And then you may think about a very expensive road bike, or perhaps a recumbent. Most of us have gone through this cycle - don't be a bit surprised if you do, also. Many of us own multiple bikes.
Don't ever ride a bike to get fit. Ride a bike for fun and get fit in the process. If you ride to get fit, you will not be riding very long.
My first bike was a 1998 Specialized Hard Rock mountain bike with slicks (smooth tires). About $300. I rode it for thousands of miles, and still ride it. It was the bike I used for my first "Ride the Rockies" 353 mile week-long tour of Colorado passes in 1998, several months after I started riding.
FYI, here is an important thread on osteoporosis, which is associated with bicycling.
Most of all, have fun. Use this forum for advice and encouragement. Introduce yourself when you feel comfortable.