If you're so poor you can't buy new underwear, then turning your ass into a billboard probably isn't beneath you. There's this new service in Japan that's offering to send dudes up to seven pairs of underpants--provided they're okay with renting their bottoms out as billboards, since ads and logos will be plastered on the back of each pair.
Unfortunately, you have to have a good handle of the Japanese language because the site that's offering the free pants is in Japanese. I'm not even sure if they ship outside of Japan since I can't understand a damn thing on the site and Google Translate is doing a crappier job than usual.
Check It Out: Free Pants