There are some disadvantages, of course. Cash flow is a hideous, insomnia-inducing nightmare - you have the income on paper, but suppliers need paying before your clients pay you because as a new business, you don't get the same payment terms as you would if you were Harper's Bazaar, say.
There's also the tension between fulfilling your obligations to existing clients whilst also finding enough time for hunting down new business. And there's also tiny things - you can't be off sick - firstly you don't have time, and secondly, you don't get paid. Yesterday I had a migraine and had no choice but to go to bed in the dark. I'd consider myself to be pretty stoical - I've soldiered on in the past through laryngitis and pneumonia (though that got me in the end and I did have to take time off) but migraine is so thoroughly incapacitating one can do nothing other than go to bed, try to keep the drugs down and wait for it to be over.
Anyway, fortunately I'm much better today and can get on with work.
And the work I couldn't do yesterday will have to be done over the weekend.