I would not pay too much attention to that. write your story and make it as long as it organically grows.
If it's a short, coherent story line, you've got yourself a novella, if it goes on and on and meanders through time and space and mixes a lot of story lines, you end up with a novel. A novel goes for a broader abroach. However, there is no clear definition of length for the short story (though that one is supposed to be read in one sitting), novella or novel. It is the content and style that defines them.
If you hope to sell your book to a specific target group to primarily make some money with it, do some market research: What does the kind of story you want to write usually encompass, how long are they, who reads them and what is usually successful, etc.
If you want to write because it gives you pleasure or because you perceive it as your calling and you want to become an artist, forget about all that and follow your gut. If you don't trust your gut, you can still try to learn from some writers you admire.
By the way, I think there are a few writers on the forum who even have a little group of their own going on.
