travis, really depends alot on silverprices. what throws things off is there's often a turnaround time of 7-10 days so silver prices can change alot in that time. i was dealing with a lady for a while who was getting me monster boxes for $1 over spot. for a while it was good. my margins were so good i didn't even bother selling on ebay, Id pay her a dollar over spot then run to the coinshop where they would cut me a check for $2-$3.50 over spot so i making like $1500 just driving to the coinshop. well this lady said she was hooked up with the mint, she lied, turned out she had a friend who owned a coinshop and was buying in from the public. she oversold and i would have to wait a week or two to get my shipments. in that time silver went from like $28 an ounce to about $21 an ounce and i got hammered. lost most of my profits from the previous weeks but still was up a bit.
one thing i do notice on ebay is ebay prices take about 5 days to catch up with teh market so if silver prices go up you will not reap those rewards if they crash you got a few days to dump your silver before prices go up.
you need at least 12k or 13k to get into this business as you have to buy a monster box if not a few. some people also choose to get their box graded beofre selling it. as long as you get some decent graded coins you wind up making alot more, if you got crap coins you lose money as its not cheap to get stuff graded