Generally the price in the market is quite similar, so if you see a considerably low offer, ask the company or person for more information and see the container in person. It's probably a fraud.
Many of the frauds do so through Facebook, creating fake accounts and placing the product on the marketplace. Normally, they do not have friends or information about any activity on their profile page. Also his profile photo is blurry and is not his own but from the internet. So if you contact someone like this make sure they are legitimate and ask to see the container in person.
When the purchasing process is light and they try to make you pay as soon as possible to provide you with more information. If it is outside of Puerto Rico and they do not give you details of shipping, delivery and possible additional costs for sending the container to the country, possible it is a fraud.
Most ask for some type of deposit of half of the total, it can be through PayPal or direct deposit. Paypal they can ask to transfer them through the "friends and family" option, since when doing so under that option there is no possibility of claiming the money once they realize the fraud. When they ask for Direct Deposit, which is into the bank account, they don't disappear quickly. They wait for the due days to pass so that the money cannot be claimed.
Be sure you have all the information of the other steps and the information that they are legit.
However, it turns out that after the deposit there is a lot of confusion in setting the delivery date, communication becomes more and more complicated until it disappears completely.
Companies or people outside of Puerto Rico that have low prices including delivery are usually fraud. Since you must pay extra fees to send a container from the United States to Puerto Rico. Companies do not sell retail containers to Puerto Rico, unless it is wholesale.
If you make the purchase in Puerto Rico, ask to see the containers in person and choose the one you want to buy.
If it is outside of Puerto Rico, ask a family member or friend to go see the container in person
If you are speaking to a salesperson via call or text, ask them to see the inventory in person and close the deal in person. This way you know the person and the place where they are operating. You can see if it is a real business or not.
Find information about the company that is selling the containers. Companies normally have pages on social networks, check their activity and if they have a website. Analyze how trustworthy they look.
If it is a person who is selling the container is online, look for their activity on social networks. Check if he has sold things before and ask him why he is selling the container and where he has it. Ask to see him in person and record all activity.
Request detailed information on the purchase and delivery process to Puerto Rico. Check if other expenses are necessary and if they must provide you with any real documents.