If you plan on buying large sets off auctions and busting them up, a little advice: BE CAREFULL. Although most adds are not “lies” they are often misleading. As a rule we think of it this way:
If the lot is being sold by a dealer or someone who sells a lot of singles, you are going to get the rare cards that are not getting enough by themselves so the are bundled up in large sets just to move cards.
If the lot is from the guy “selling my whole collection because …” do a seller search and see if he has sold any “big dollar” or “power” cards in the last 60 days. If so all you are getting is the junk left over (same as above).
We did what you are considering and found it to be a lot more work than it actually netted, and then you also take the risk of it not even getting anything.
Most sellers who are truly selling large sets to get out will often set a reserve to protect their investment. They often set it too high and then it often will not sell for what they asked. When the auction ends without a winner, email them directly and see if they will work out a deal. The last time we did that, we got a 7000+ card collection for $450 including postage. After fees, the cards we did sell put $495 in our pocket, about 250 or so above average uncommon and rare cards for my personal collection, and 2 cards that I still have never figured out what they are.