A common question is whether one needs an onward or return ticket for traveling to South America. Immigration officials at the airports almost never check to see that you have a return or onward ticket for traveling out of their country. So, you will not face any hassle at border crossings. However, the problem is usually with the airlines which may refuse boarding to a passenger without an onward ticket. Airlines differ on their policies but be prepared to encounter this difficulty in case it comes up, which usually will mean buying the cheapest refundable ticket out of the country.

For example: if flying into Buenos Aires, one can always buy a refundable ticket from Buenos Aires (EZE) to Montevideo for about $80 US. Once in Buenos Aires, have the ticket refunded.