Just another learning bass question here.

I've been playing guitar for about a year and a half now and would like to start learning bass as well.
so can someone give me advice on what bass to buy (and whether to get a p bass or a j bass)

If you're trying to decide between a P or a J bass, it seems to me you've already decided what you want to buy; a Fender (/copy). What sort of sounds are you looking to achieve, and what sort of music are you looking to play?
Spare a Cow
Eat a Vegan
I'm interested in creating unique sounds and I am looking to play Alt rock mostly.

As a side note my guitar is a Yamaha Pacifica so would that influence my choice in bass?