First thing that comes to mind is: "one man's junk is another man's treasure...."
I'd yank that back floor mat and assess the floor---those things are a known rust incubator. Next would be a very thorough under-body visual inspection for rust anywhere. There will be some but how much and where would be a concern.
Honestly though I'd pay $1400 for that van as is. Yes it looks somewhat beat to hell and back but as a rolling chassis for low dollars the visible repairs aren't a huge issue. Motor mileage isn't too much a deal breaker either.
Yes spending more would most likely yield a "better" vehicle but how much better really? Having now owned a worse condition '97 along with a '00 and daily driven '03 I'll say body-wise the '97 > '02's seem better. Could be just my perception and experience but looking in the scrap yards I see many, many earlier E-Series still in good shape, even up north here.
In fact that van might be driven off the lot for a cool $1200--act quickly if you're up for a bit of elbow exercising!