Don't be greedy - customs isn't as likely to notice 20 shirts packed in luggage as they are something like 5 iPhones...
And as been discussed before here somewhere, used clothes from places like North America and Europe are worth quite a bit here. I know of businesses in Paraguay that pay the right people to get clothes through charitable donations that have been sent down to the poor (and I'm pretty sure places that sell used American clothes here [there are some] surely have some inventory that comes from similar sources) because quality, imported used clothing is valuable.
It's illegal to import used clothing for anything other than personal use in most, if not all, of SA. Ostensibly to protect the textiles trade in SA from "unfair" competition, so they can keep cranking out their low- quality, often last a month or a few washes clothes in peace.
In fact, the more I think about this idea, the more I like it and see ways for people to do this. Could be somewhat risky...but there are many, many "clothing shops" in Buenos Aires that have fairly inexpensive clothing that is available in many stores here (better than the cheapest, but not as good as good-quality imported used OR new for that matter) - but are run out of private apartments.
I've been a number of times with my girls to take a look at deals they've found through Facebook or other social media sources. In fact, there's one woman who does this about two blocks from where I live in Recoleta. She has a two-bedroom apartment that she rents specifically as her "showroom". It's on the 6th floor (if I remember correctly) of a decent building with full-floor, but not very big, apartments. She has to come down to let clients in. One room is where she hangs the clothes, on mobile clothes racks, and the other an office. It even has a kitchen. Heh. But her prices are very good and she has a decent variety of clothes that aren't too poorly made at a decent price.
She makes a fortune. But she's been there for at least a couple of years and hasn't had any problems. I've never felt comfortable enough to ask her how she operates.
There are other people who are like traveling salesmen in that they literally bring a couple of bags of clothes to your apartment - when called of course. Usually those aren't the best quality, but there are some surprises - but always low prices.
So, if someone wanted to start a business selling button-down cowboy shirts, they could bring a quite a bit of used clothes at a steal (I've seen the prices on clothes at Goodwill, and there are some absolutely amazing deals available) from North America, Europe and other places and sell them at the same prices as cheaper clothing here and probably not be able to keep enough stock for demand. Advertise through Facebook, pass out cards to people at parties and bars. Maybe offer them on Mercado Libre.
For crying out loud, that's such a better business than teaching English if you have the head for it. You just have to do some research and see how you can get enough clothes down (if I had to, I know enough people that travel here, and they know enough people, that I could get something once or twice a month easily, but maybe not much quantity). I think someone's previously mentioned a service that lines up mules traveling down here with people who want things here. If you could find enough people to bring things down at a relatively low added overhead (almost certainly cheaper than paying for a round trip ticket to bring down a load of clothes, though of course any time you're back home you take advantage to bring some down), I think you could easily beat what you would earn with teaching English.
Think about tax issues and such as well, but you have some of the same problems with teaching English that you'd have to overcome with selling used imported clothing, the major difference probably being the actual importation of product (and we're probably not talking a ton of clothing, not a get-rich high-volume business).
It's much easier to sell quality clothing than it is to find clients teaching English. And probably more lucrative and allowing more time off. Think of this - even English teachers need to buy clothes, which includes pretty much everyone, but the market for English teaching services among the population, while not small, is probably not as big.
Unless you like to work in the corporate world, in a controlled environment and are lucky enough to land a job with someone like Bradley and his setup (although I don't know anything more than what he's written about). I can understand that desire - I was in the corporate world for a good twenty years, and various levels and sizes of companies in two different industries. I'd never go back - I'd probably end up living under a bridge first, heh.
But finding a good position like that here is probably not going to be easy for someone with little experience. Then you're stuck with hustling clients or hooking up with a school that pays relatively little and demands a lot and treats you like crap...and so on.