Making a game is not something to be taken lightly. There is a serious amount of work in developing a text based game (speaking from experience). And NancyJ is correct. They are not just some scheme to make lots of money. At most you can expect just a little bit of extra cash but nothing significant. Only a minority of games are successful enough to make decent money out of.
But there is always the aspect of making games for fun and to learn. That's how I learnt PHP properly. I read my books and stuff but couldn't think of anything to make. So I thought "Heck, I'll make a game for the hell of it". Took a while but the extra knowledge I gained through development was very valuable