Ford 7.3L Power Stroke (1999-2003) :: Cranked For About 10 / 15 Seconds Before It Sputtered And Tried To Start But Quit

A lady friend of mine got a '99 7.3 CCLB auto dually in a divorce. She doesn't drive it but starts it once a week and yesterday it wouldn't start. It cranked about 10/15sec (after waiting for WTS light to go out) before it sputtered and tried to start but it quit. Then it cranked another 10sec or so and the batteries died. It was about 85deg so it should have started w/o GPs.

Watching the voltmeter, GPs seemed to draw current. There's a lot of corrosion on both batteries so I know that needs to be cleaned up. Assuming the batteries aren't shot, after cleaning the corrosion, is it safe to hook jumper cables to a car to charge the batteries, but disconnect the jumper cables before starting the truck? Or should I use a plug in AC charger? I've never jumped a dual battery vehicle - not even my own 7.3.

She wants to sell it but it's in pretty rough condition - possibly normal for that age with 160K on a work truck. It was used in a business she had with her ex. The valley of death has some wet fuel in it and there is a film of diesel on the fuel bowl, fuel lines and wiring in the vicinity. I could smell the fuel before I opened the hood or tried to start it and it hadn't been run in a week. She says it runs fine and uses no oil but is always rough to start. It rolls rather than barks to life. It's bone stock with flat factory downpipe and airbox.

The engine cover is missing. Connectors and wiring on top of the valve covers appear new. She looked up the value and says it books for $7200 on KBB in its current condition. It was always parked in the sun here in Albuquerque and it shows. Body looks good as far as no rust or dents, but the white paint is faded (flat looking) and the blue interior is also pretty rough with 40/20/40 front seat and cracked dash. If I get it running I'll post it in the for sale section if she doesn't find a local buyer by then.