You are required to register to collect and remit sales taxes if you are selling $30, 000 annually.
While Revenue Canada will overlook occasional 'garage sale' type income, if you are regularly selling, you should be keeping records and declaring any income.
Remember that the money you take in is offset by the money you spend -- procurement costs, postage, sales taxes (you get rebates on those), eBay and PP fees.
Keep careful records. Revenue Canada tends to think the worst.
