You take it to the scrap yard. If they give you money for it, it's positive.
If they charge you to take it off your hands it's negative.
Specifically if it was an aluminium bodyshell that had been stripped of all plastics and with no tyres or battery then it would have a positive value.
If it was rusty old steel full of unrecyclable plastic, then it would probably be negative. Cheers
Greg Locock