NOTE I learned from buying new boat applies to RV, used or new. The operations and owner manual are critical to use. BEFORE you close deal, make part of closing/title etc this. ALL operations/owner manuals will be placed on or beside the item(S) they apply to, work with, etc. Then each item will be shown by seller as to operation, maintaining, manuals etc until you KNOW, or both of you KNOW how to operate/maintain them.
If you do not do this, you end up with a stack of paper that may or may not be there when you need it, may or may not apply to your model or they just do not have the manuals. You will some day find you need the manual, that you never got, so insist on manual next to item and remove when you know how to operate. Kind of takes care of two critical items at one time.
I learned lesson the hard way on a diesel filter on engine that seemed to only shut off when nearly wrecking place while docking, usually in front of hundreds of people whom wondered how come I even allowed to own boat, much less use it. Seems the valve I thought was shut, was not 100% so and sucked air when it felt like it at idle. I found that out when I bought missing manual