Aside from the fact that consumer decks only have two tracks in each direction. they usually have a half track erase head , making it difficult (but not impossible) to record stereo tracks at different times.
Look for a used Tascam 234. You can select which track you want to record on. I could be wrong but I believe Tascam made a stereo deck also, that you could record on one track at a time. I just don't know the model. That is if you want to overdub or lay down seperate tracks. Hmmm, maybe I missed the point
fitZ