You work at a shop and can't afford it? Umm, no. Pro deal, staff discount, beg it off someone else at the shop, buy a cog second-hand off a customer, etc. Christ, just get off your ass and change the cog. Otherwise trade your bike in for one that you can afford to maintain. I'm not even goiing to bother with the brake notion because you're invincible for a few more years still.

You do know how to stop the bike on one of those downhills after you drop your chain, right?