If you are concerned, speak to an accountant.
If the CRA considers what you do to have a reasonable expectation of profit, they might consider it to be business activity, even if you claim you are only collecting. Buying a lot, and then breaking it up for individual sale is business activity. If you're keeping half the lot for your own collection, and half to sell, it might still be considered business activity. I don't know.
Google personal use-property CRA to see the rules about selling your own property.
Even if you determine your activities fall under personal use property, you should still keep records of your purchases in case you get audited. eBay is all on the books these days so theoretically if you have four or five figures sold on eBay over a year, that's all going into your bank account via managed payments.
Depending on what your personal income is, and how little profit you're making on each individual item, it might make sense to run your eBay account as a business. If your profit is low enough that the additional income tax you will pay on it is small, you can voluntarily register to collect HST. eBay already collects HST on every transaction, so there is no downside to doing this, other than record keeping. The upside is that you can claim a tax credit on the HST you pay for anything business related (cost of inventory, supplies, eBay fees, business use of a portion of your home, etc). Because eBay is going to collect HST on your transactions regardless, you will get a refund at the end of the tax year for all the HST you spent on your business.
Keep in mind, I am not an accountant. The above is based on my personal experience and shouldn't be used in place of speaking to an actual accountant. The above post may be completely incorrect, because I am not an accountant. Did I mention, I'm not an accountant?
