Do NOT allow the seller to use a courier like UPS or FedEx. Their fees seem reasonable to the seller, but you will be charged, in addition to duty and sales taxes, a 'customs brokerage fee' of $25 or more.
Best is USPS/Canada Post shipping.
Canada Post and the CBSA have a practice of ignoring low value (under $100, sometimes higher) and smallish parcels. They seem to understand that if the fees collected are less than the cost of paying the CBSA officer to assess the item, what's the point?
http://www.cbsa-asfc.gc.ca/trade-commerce/tariff-tarif/2013/01-99/ch97-2013-eng.pdf
If your item is provably 'antique', and I think in Canada that means more than 100 years old*, I read page 3 as saying there is no duty. But if the value (the amount you paid) is over $18 USD /$20 CDN you will be charged sales tax and a service fee of $9.95, which will be collected before the item is turned over to you.
And it's not a 'gift'. Forget that.
Your best bet is the much despised Global Shipping Program. If the listing includes this statement
Customs services and international tracking provided
Then you will be told the amount of duty, shipping, tax and service fees you will be required to pay, before you click to pay for the item. Nothing will be due on delivery.
*But Britain and Europe use the pre-Industrial Revolution date of 1830.
