1. It can be--whether the income from one's games is enough for a developer to live on depends on how well the games sell, how much they sell for, and how high the developer's expenses are (both living expenses and expenses developing the games). It's a challenge to make a living off of game development, and not everyone can manage it. I hope to eventually reach a point where I can count myself among the lucky ones who succeed at this.
2. Nope.