This is the relevant section (see below) to your question, it lists 9 characteristics of a business carried on for profit, i don't think any are necessarily definitive, if you meet the majority of these criteria you should be in a defensible position.
In determining whether you are carrying on an activity for profit, several factors are taken into account. No one factor alone is decisive. Among the factors to consider are whether:
You carry on the activity in a businesslike manner,
The time and effort you put into the activity indicate you intend to make it profitable,
You depend on the income
for your livelihood,
Your losses are due to circumstances beyond your control (or are normal in the start-up phase of your type of business),
You change your methods of operation in an attempt to improve profitability,
You, or your advisors, have the knowledge needed to carry on the activity as a successful business,
You were successful in making a profit in similar activities in the past,
The activity makes a profit in some years, and
You can expect to make a future profit from the appreciation of the assets
used in the activity.