Canadian corporation doing business in USA
Any suggestions on how to do this? or other recommendations?
Generally speaking, since your business model is about buying and selling in US I would suggest you do it using a US entity, for example an LLC domiciled in Wyoming or Delaware.
Depending on the type of goods you buy and sell and states you ship to and from you might be required to obtain Sales Tax ID in those states, and in some cases in order to obtain sales tax ID you might be required to register your LLC as a Foreign Entity.
To give you a more precise answer I would need to know more details about your business model, such as what type of goods you buy, do you resell them as a retailer or as wholesaler, whats states you will trade in (buy/sell), etc.