EVERYTHING is possible. That's the problem in answering that question.but I am just interested in what is possible
You can be anywhere from losing thousands of dollars to making millions of dollars.
There are really too many variables to say what kind of profit can be achieved.
It's not like a salary job where you can say "Dental Assistants in Minnesota make an average of $50,000 per year". It's a sales job where you control the outcome (somewhat). So you could make $1 or you could make $10,000,000. Or you could lose your shirt.
It's all possible.
The thread that Kris linked to above is the main one that discusses this in great length.