I'm a freelancer, slightly different to what you're suggesting, but I run my own affairs and much prefer it for a number of reasons.
If you go VAT Rated split off your VAT money to a separate account when a payment comes in - its not yours and the VAT man plays rough.
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You haven't chosen the best time ever to do this have you?
In my opinion this is the single most important bit of advice in this thread (so far). Never be tempted to spend this money, I would guess that more businesses get in trouble this way than any other.
It always used to be that the revenue guy was a bit more flexible than the VAT guy. They're the same outfit now, so bank the money and pay it on time.
Ive been employed in a pretty safe office job now for 12 years, worked my way up etc. but becoming disillusioned with working for other people.
Ive been considering buying an existing business for a while, though havent seen one I like the look of yet.