My suggestion is to browse at Craigslist and look for the BlackBerry Bold 9000 for $80-$120. Reliable phones. Meet the seller ALWAYS at a public place. I usually try to meet them at a local library or mall.
Either the BlackBerry Bold 9000 or the Samsung Focus make solid choices for a loaner. If you want, just get an older iPhone like the original or 3G. They go for pretty cheap too. Then when you have the iPhone 5, resell them back. It is that easy. The guy who bought a Bold 9000 paid me only $10 more ($90) than what I bought it for. Then I told him to sell it for $120-$130 which he is doing right now. Nobody is losing here. Just make sure the phone works.
That is all I do with CL. I buy used phones for cheap and if I want my money back or get bored with it, I sell it for the same or above the price I bought it for. I really have nothing to lose. Smartphones for $80-$130 are usually a good deal for most people and have high resell value. Craigslist offers almost like a FREE RENTAL for these different platforms.