Too old to train?

I’d like to train as a commercial pilot, but I’m 40 years old. (I only recently discovered an interest in flight through gliding.) If I financed my own training, what would my job prospects be like?

I’ve read articles in Flight magazines suggesting the market is picking up and there may be a big increase in demand coming up for pilots. Do these kind of views come from organisations like training companies with vested interests, or are they widely held?