Customs duties on used underwater gear

I have seen pre-owned items for sale from outside of USA and I am interested but do not know about the customs duties and tariffs involved.  I would really appreciate input from members who are knowledgeable or who have purchased and received items within the USA.  I would like to purchase a used housing and lens from a Canadian seller but I would like to know what to expect and whether it makes sense to proceed.

Thank you in advance. 

I have shipped goods to Canada and US together with a customs form. Take into account that you cannot insure something for $200 and then declare zero value at most you can mark it as a gift and then the buyer takes chances

On two occasions I have sold items they have arrived on time both times and no custom duties have been charged

On the receiving side however I have always been charged customs duties on imports from Japan, China and Switzerland this does not bother me as I have a VAT and EORI number however it indicates that in essence depends on the receiving country more than where you send from

Thank you, I really appreciate your response.