bass amp or guitar amp?

I would get a guitar amp, but that is just me. But what ever you do, do not play the bass through the guitar amp. (guitar amps, aren't made to handle the bass vibrations). But your right, Bassist have a better chance to be in a band, due to the lack of bass players, but if you can play guitar, you can play bass. And usually, sometimes, some bands, when they get a bass player, they will let them use an old bass amp that some one has in the band, to let the bass player rehearse with.