My advICE would be to go for it mate and dont let your age be a mental barrier to your workouts. Things like taking care of your joints by avoiding certain exercises like doing things "behind the neck" and really taking your time to warm up and (stretch) cool down. I'm 26 and have been training for over 12 years, and my body feels different than when I was younger and I know that I have to be a little bit more careful; it must be even more so for a guy pushing 50, however, some of the strongest dudes in my gym are older wiser ones.
All I'm really saying is look after yourself more than the younger guys, but dont set your sights any lower, you CAN do it mate!