I know some hate grading, but I do it myself.... I keep sealed games in my collection which i like, and i sell others.
I like making money with it, but its not always easy.... you can have sealed games that looks nice, and you make them grade, and you only get , let say 80 of grade ( with VGA ) . When your games get lesser grades, you cant sell them for big prices. So sometimes its not a loss, but its a waste of money that wont get you profit as you expected.
Also, one thing i should mention; I've collected sealed games that had stickers on them... you can use gasoline (lighter fuel) to remove stickers and it works great , but sometimes it leaves a trace on the spot.