Apart from knowledge it depends how busy you are.
Waste a day at auction and no wages for that day.
however im perhaps well placed to answer this question as before i started window cleaning I was an auction buyer for a medium sized dealer group
assuming you manage to find a good van ... with history ... nice condition ... no issues etc you will have to compete with everyone else wanting to buy this van .. people like me ( well used to be me ) who need to buy it for a living you will pay top dollar for it as no bargains in auctions these days as used supply in drastic shortage so prices are high ...
THEN .... you will have to pay some charges for the pleasure of buying from the auction ... these are from memory and apply to larger auctions such as ADT ... you have log book transfer fee @ £25 then the buyers fee which on a £5000 van is £300 to £450 give or take ...
so by the time you take all this into consideration its prob not worth hassle esp as you may buy a pile of rubbish after all your time, hard work and expense.
If you dig around on autotrader you can buy same van cheaper at a dealer with all the legal come back and no hassle or try these
http://www.northgatevehiclesales.co.uk/ ... ex rental stuff but seems cheap enough.