Since you are new to the forum you probably haven't had the chance to read about the various items expats have brought with them to resell in BA to make some extra dinero. Most of the posts have been about iphones and other electronics, but there's always a question about how much to bring without having to pay the 50% customs duty.
Perhaps a few members who have recently been "rewarded" for their entrepreneurial efforts will share their stories. That might give your son and his friend some ideas. Bringing a suitcase full of pre-owned Ralph Lauren and other designer dress shirts is what I'd do if I was coming from an area with a lot of thrift shops and "high-end" donors (D.C. Chicago, San Francisco, etc). Even if it is a "crummy" way to earn extra money in Argentina, it is better than not having the extra dinero.
PS: If your son sells anything on Mercado Libre, my best advice is to only meet buyers in a public place (coffee shop) and always check the currency to be sure it's genuine. He will be able to sell more quickly if he offers to sell "sin compromiso" and which means the buyer can decline the purchase when he sees the item in person and does not want to complete the sale.
You can use the advance search here to find topics that discus selling on Mercado Libre. Enter "mercado libre" in the search box and search only in titles and have thee results displayed as a "topic list." Click on the sprocket next to the magnifying glass to get to the advance search.
