I think it's more about the willingness to just put the the time in, rather than sheer talent. He's CONSTANTLY checking for new listings, has auto alerts set up so he gets notifications for certain listings, even just picks stuff up because it's a good deal and would make for good trade fodder.
Hell.. he even sets up trades using trades he hasn't even traded for yet.. and pulls it all off. Like... awhile ago he was after this zero turn lawn mower.. guy with the mower didn't want to trade for whatever he was offering.. so he asked what he WOULD trade for.. guy tells him a wood splitter.. my buddy scours listings looking for a splitter.. finds a splitter IN THE PICTURE of a listing for SOMETHING ELSE.. messages the person.. and ends up trading for it

then he goes and gets the zero turn.
Then he traded the zero turn, a non running go-kart, and a pancake compressor for a Meyers Manx and a Suzuki sv1000 which he rode all last year. Traded the bike for a beat up 04 chevy and a 2015 mountain sled, traded the mountain sled for a supercharged 06 chevy, traded the bike and something else for a 74 charger... it's really never ending lol.
I personally couldn't deal with it. Everyone on marketplace is a total jackass and I hate having to deal with them.