Apart from an Escort van that I bought new (many years ago, it's P reg) I have bought all my vans 2nd hand.
Notable bargains were a W reg Berlingo, 50,000 miles, from a flosist, perfect condition, £2200 and an absolutely immaculate R reg Astra, 115,000 miles for £750
I would advise an Astra van rather than Escort, as even the R Astra looks a modern shape, and is certainly a more modern van to drive. Pay less than £1000 for a good clean one, and then pay for some really eye-catching vinyl graphics. Then again, the Escort has more headroom, if you were thinking of a water tank.
Park your van in a prominent place (don't hide it on someone's drive, leave it in the road and carry your equipment) and it will pay for itself in advertising.