Heard there are great second-hand musical instrument stores - where are they?

Looking to furnish a studio apartment on a student's budget... so, hoping to get hold of some second hand furniture. Are there any good websites/shops in Buenos Aires dedicated to …

I need some input on how to buy meat in Buenos Aires. What cuts to ask for (translation English to Spanish would help). Where's the best place to go to (market/butcher/supermarket) …