i dont know about free man. I do know that you can get a digital 4 track with a build in drum machine for 200-300 dollars. It has an effect that make a guitar sound like a bass as well. The model number is BR-532 and i think its made by boss.

Or, one thing I used to do before i knew what a 4 track was....

Got a cheap casset recorder with an external mic. Recorded a track on it while playing through my amp. I then took the tape out of it and put it into a tape deck with loud speakers. Also I put a new casset tape in the tape recorder (with the external mic.) I would hit record on the tape recorder and hit play on the tape deck, and then play the second guitar part along with the recorded part.

It sounds very poor quality but you can hear how the notes interact. You can also hear how the rhythm interacts if you use a metranome.