I have been using the OP's methods for a few years and have been lucky enough to find some great deals. The best deals I have found are on Facebook shop and swap type groups. It's going to sound bad, but some lady selling off her son's Lego collection is the best way for me to find good deals. Recently I got the whole rock raiders line, one of the Indiana Jones sets, a few starwars sets, about half of the Atlantis line, most of the Ninja turtles line, and a few other sets along with a classic yellow Lego storage container full of minifigures and accessories and about 20lb of loose Lego all for $100.00 CAD. The second hand stores and antique stores near me usually also have small bags of Lego for decent prices, maybe 5lb for $10.00 CAD. It's really all about making the rounds and checking local online classifieds, Kijiji, and Facebook groups regularly. I did have one bad purchase recently though. I bought a bin of Lego about 25lb for $200.00 CAD and I didn't notice the problems with it when I was buying it, but once I got it home there were teeth marks in probably half of the Lego. And one of the minifigures legs looked like it was used as a piece of gum there were so many chew marks in it (and in sand green!). Maybe the kid thought it was mint gum (haha). But one bad score out of probably 30 or more isn't so bad.