You can help yourself greatly by buying a caravan magazine that has the weights of the various models listed and the max weight rule that applies to your vehicle. A very simple regulation.
Once you have rhe permissible caravan models listed you can determine which size and layout suits you.
There’s rather a dearth of caravans for sale right now so you might have to look further afield than you would like.
You should definitely have an experienced person to inspect before you buy because caravans can and do rot and tents deteriorate quickly as well.
You can have movers fitted after you buy your van at a cost of about R14000 depending on who does the fitting. If you only look at vans with movers already fitted you will limit your options severely.