Hi folks, i'm a trumpet player from Argentina. I'm thinking about buying a trombone to play funk, but i've got no clue about sizes and brands. Can anyone give me a hand on this subject?

My suggestion is to find a student/beginning horn in good condition and learn to play it well enough to decide what characteristics you want in a horn for the music you are playing. A Yamaha TR354 (for example) in good condition is great for learning on. There have even been pros who used them as their primary instrument.