Hi and welcome. That’s quite short notice. Hopefully others will be along soon to offer advice.
In the meantime, is a private sale or via a dealer? If dealer, is there any warranty? If private, Have you had an inspection from someone like the AA?
Have you checked everything works (the downloads section has useful info)... ?
that will give you specific areas to look at (leisure batteries, auxiliary heater, fridge, tap / pump, hydraulic roof, gas connector / pipes, cambelt and pump)...