The only TLD with a reliable market is the .com. You could also make money off certain ccTLD, but those are a bit trickier. Just as a reference, it's not uncommon that clients that are willing to blow five- or six-digits on a .com won't even pick up the .net for the registration fee, and then .net is the second best gTLD (after the .com).
Does that mean that .net is worthless? No. It's just very difficult to find buyers for. The .click is a worse. A lot worse.