Well I do think more people of all ages should play tennis. It's great fun, social, good aerobic exercise, and unlike golf doesn't take up too much time, typically an hour or so. What's better is that you don't really think about the exercise element because it's primarily fun. In my opinion this is in stark contrast to jogging and gym work where it takes mental commitment and is hard to keep up regularly. And it's not a contact sport nor involves extreme strength so injuries are exceptionally rare - tend to only occur at professional levels.
All you need is someone to play against, a friend or someone else who wants a bit of exercise and fun. You can start by just hitting balls back and forth over the net without playing games at all. Gradually co-ordination improves and you get more and more fun from it.
Joining a club is a very good idea and it's then easy to get into a regular playing pattern and finding people your own level, nice social scene, coaching etc.
I've been in a tennis club for about 12 years now after starting by messing about on public courts. It's weird, but even though I've obviously aged since then, my tennis skills have improved in that time beyond all recognition. This is without any major commitment other than having fun playing regularly and the odd bit of informal or formal coaching. It's very rewarding to see your skills improving from year to year.
Tennis courts are something we are not short of in Ireland. You would be amazed by the number of clubs around, often hidden away off side roads and cul-de-sacs. There are plenty of public courts too. You need very little equipment other than a racket and runners.
Tennis is fun and fitness - and in that order of priority!