Javex.... Revenue Canada and Minister of Finance (PST) don't know what hobby income is.... If you made money (a profit) or sold none personal assets, you have to pay tax and collect and remit sales tax (I am speaking Ontario here).
In terms of getting a rebate on PST... yes and no... well not a rebate as much, but you can get PST money you paid on goods refunded. Goods you purchase for resale, providing you have a PST number, can be purchased PST exempt from your supplier providing you have provided a PST exempt form. If you purchased any goods for resale, but ended up paying PST on them, this can be deducted from the PST collected on sales to be remitted to Minister of Finance (but keep receipts and documentation in case of audit).
Unlike GST, PST paid on items for the operation of your business are not exempt, nor do you get a rebate or input credit similar to GST. (ie, the computer you bought to run your Ebay operation is not for resale, but a consumable used by the business and it is neither PST exempt, nor can you deduct the PST paid as other than a business expense).
However, if you buy any goods and pay sales tax on them that are used directly to sell a taxable item, then you either can a) have the supplier sell them to you as tax exempt (again providing a PST exemption form) or b) if you paid PST on the item, deduct this PST amount from your remittance. An example would be say if you ran a coffee shop and obviously sold cups of coffee. You go out and buy styrofoam coffee cups and napkins and end up paying PST on them. As they are used in the sale of the taxable item, you can either purchase these items as PST exempt or deduct the amount of PST paid from your remittance.
However the cash register you bought to register the sale, or the cash register tape to document the sale are neither PST exempt or can you deduct the PST paid as they are not considered items for resale, but rather consumables used by the business..... clear as mud I hope.
Jeff