Hi David and welcome to MHF. as said a bit more info is always useful, but being new we don't expect you to know too much, and you've had the sense to ask on here.
Our first van was an Autohomes explorer on a VW T4 chassis, and it was one of the best laid out vans we've had, just a bit cramped for longer trips.
As for your questions, perhaps the best person to ask is the person selling it, unless it's a dealer, but most do have water tanks and a leisure battery.
Before buying it perhaps you might want to ask a few more questions.
Older Motorhomes can be really good value, but they can also be a nightmare if you don't know how to examine one properly, damp is the biggest issue, so ask away, and if possible take someone experienced with you, or better still pay for the time of a mobile Motorhome technician, it could save you hundreds or even thousands of pounds by not buying bad one,