Out of all of these ideas, I only like the Legos one but not the high cost "buy and wait, then profit" because in 10 years, they might be worthless.
My son is home from college and since he doesn't start his summer job till next week has been going through the old legos. Everyone in the family bought both my kids lego sets for birthdays, Christmas, random in-law and grandparent gifts. We now have about 10 cubic feet of them. No, I mean literally. He's been going through them specifically finding Star Wars figurines, finding all of the accessories and selling them. An average figurine that he puts together brings about $20 with free shipping. I know we have a few Boba Fetts hangins around (only kidding), but in any case, every single piece has the kit number listed on them, so it's just a matter of pulling out the magnifying glass and loading up the box with star wars pieces. He's told me that a standard box of random pieces is worth $15-$20 where a box of star wars pieces are worth $150 to $180. He's done sales before with nintendo games picked up at Goodwill and flea markets. His best sale was to pick up a bucket of games for $5 and have a rare one in there that he sold for $105. This is labor intensive, however. With the mass quantity of pieces we have, it can take him hours to find a complete figurine with all the accessories.
Also beware of eBay scammers who sell bulk star wars figurines when in reality, they only have the body and the rest of the pieces are from random other non star wars pieces. Wrong arms, head with hair, random legs (remember the kit number is on every piece) make them worthless crap. Well....$1 a pound crap.