I think you are asking the question in an awkward way. "What can you buy to scrap and make money?" The answer is simple, but more complicated than you think.
The simple answer is what ever you buy and pay less than scrap value for.
The more complicated answer is you need to take the time to learn what things are worth. When ever you pay for something you HAVE to know what you are going to get for it. If not, you need to pass. Many times you will get lucky and make out okay, but it is the few times that you are wrong that can kill all the other profit.
I often buy with the intention of reselling, but I still rarely pay more than I can get in scrap. This means I often pass on things that others would buy, but I never lose money, I always show a profit.
I usually don't buy from ebay
, there are too many people that are looking for scrap which drives the price. If I'm going to buy it is usually from online or local auctions. There is never one item I can think of that I could continuously buy and pay less than scrap for, but I always find a variety of items with a good value that people have no interest in. This changes from day to day and auction to auction. This week I picked up a ton of computers. Last week it was commercial equipment. Next week, who knows.