I'd love to know where you're finding rents under $500 a month on anything in a major metropolitan area! Are you talking a studio? Or something with an actual bedroom and private bath?
The best thing about looking overseas at rents and housing prices in the large, cosmo cities is that you get a good idea of the quality of life; cultural opportunites (museums, theatre,) entertainment, and location to the central area.
I'm quite sure that I could find a cheap apartment somewhere 30 minutes outside of D.C.--but why? For me, the entire point of living near a city is to be living in a city--close to the business districts, shops and stores either in or next to your building, etc. Living in Manhattan was the coolest thing ever for me, I got a bodega @ street level and a gym in the basement. I'm not sure I would've wanted to live there if I had had to live in Queens or the Bronx--even though I sought those places out for the excellent ethnic food. I'd say the same thing for Panama City; you are going to pay if you want to live in a fashionable neighborhood that is fairly safe.
In looking for a mortgage, if you have exceptional credit in the U.S, you may be able to swing one with a downpayment of around 30%. Any of the large real estate firms, like 21st century
CENTURY21 I CENTRO AMERICA will have bilingual sites to help you out with the info. Try a little google--it goes a long way.
Cheers.