Ignoring the moral debate (because it's pointless), I will say I've dabbled in this before and it's no easier than picking stocks.
I've been to 100+ Ohio State games and thought I generally could get a read on buying and selling tickets at a profit. I'm batting around .500 and have had some huge losses.
In 2014, for example, I bought tickets for face value for our game at Penn State. PSU's schedule was soft before our game and I thought they would probably be undefeated when we played there, which would have been a huge game. Turns out they lost two in a row before the Ohio State game, and I ended up selling those tickets for a significant loss.
Same thing happened for a Bruce Springsteen concert. I'm a big fan, bought two tickets and wanted to sell two others. The venue was so big (22k) that I actually ended up selling barely at face value.
I have hit a few winners (including the Ohio State v. USC game in 2009), but they are few and far between and they cause a lot of stress.
After dabbling in this, the only advice I can give is to get some sort of "in" to get face value tickets for surefire big events. Things like the Ohio State v. Michigan game, the SEC Championship game, NFL playoff games, huge music acts, etc. Otherwise it's a loser's game.