To be honest, a lot depends upon the quality of the training. Personally, I feel that exceedingly few therapists are truly ready to go it alone without getting some experience under their belt first.
When most people qualify they think they're the bees knees and know it all, and I include myself in that, because I thought exactly the same! The problem is that unless you have regularly had treatments from an experienced therapist, the only bench mark you have of how good you are post-training is yourself and those you trained with. However, when you work under a good and experienced therapist you quickly realise you have some way to go, not just in bettering your treatments (and discovering that things are done very differently in-salon to college!), but also in how to deal with customers and the ins-and-outs of running a business.
I learnt more in my first two salons than I ever did in three years of full time college training (back when full-time was 9-6 Mon-Fri, not these half-days they now call full-time!), and although when I first qualified I would have said I knew enough to go it alone, with hindsight I now know to have done so would have been a huge mistake!