When it doesn't fit anywhere else
 #105040  by tigerstrat
 
I found a 90's lefty(!!!) Hohner Professional P-Bass copy for $100. It's a gem, I can't believe my luck, or the price.
 #105044  by wolftigerrosebud
 
I'd try to get a used Ken Smith Design (KSD) bass if I were you. Terrible resale value, excellent instruments. Put some better electronics in there and you might as well have a $2k bass -- quite well made and sturdy.
 #105052  by Pete B.
 
I bought a new Squire 5-string P-Bass (on sale) for $199 (regular like $269) a few years back.
Works fine for home recording of backup tracks and such (I've never gigged on bass).
I bought a new set of strings for it but it still has the originals on there.
It's fun to play, but I wouldn't want to be saddled up on that thing all night (I guess I'm more of a Bass owner, than a Bass player).

You could always get The Bass-o-Matic 5000
Mmm, That's Good Bass!
 #105060  by Rusty the Scoob
 
That's like saying "I need a cheap guitar". Plenty of good options out there, but I can't pick one for you without knowing what style you like or what kind of music you want to play, or even how many strings you want.

www.talkbass.com is a great resource for this kind of info, or to buy used gear.
 #105116  by RiverRat
 
I have a MIK Squier II P Bass and I absolutely love it!

If you're a guitar player looking to pick up a bass, you might consider looking at the Ibanez Mikrobass.