Colombian Immigtation

I anticipate flying out of Dubai, to Colombia, next month. Relative to my trip, I have some questions that perhaps somebody might be able to shed some light:

1. I've had two people, Yanks, that they were not asked by Colombian immigration, an 'onward' ticket when they arrived in country. Anybody here have similar or contrary experiences to that?

2. Also, somebody on another forum said that it was usually cheaper to by tickets from inside Colombia, for going to another country. So I'm wondering if it would be practical to wait til I get to Bogota and then buy an onward ticket there if they require one.

3. Also, if anybody has any suggestions on the cheapest way to cover, or circumvent, that 'onward ticket' issue, I'd love to hear it.

Regards,
Art