This company posts advertisements for shipping containers to local boards (Kijiji... etc), and will quote price and delivery well below other local businesses to lure you in. When you inquire about payment and delivery, they ask for an e-transfer payment before delivery can be confirmed, and then disappear once you've sent the transfer. If something sounds too good to be true, it probably is.
Presently (as of August 2021) there is a worldwide shortage of shipping containers due to the effects of COVID on the manufacturing of the units in China. Many legitimate resellers of the containers are having trouble obtaining units for their customers. Since supply is low and demand is high, prices have more than doubled to roughly $7k for a 40' container. When someone offers to sell you a comparable container for $4k, be safe and walk away.