I would suggest that you get a VM Squier, trick it out with a Gotoh bridge and new pickups of your preference, maybe new tuners. Put extra shielding in the electronics compartment to lower the risk of hum. I got one in that condition off classifieds for $300 and it plays and sounds like it's in the $1000 range.
If you really care about it being unlined (there are about 50 threads about that - it's mainly a cosmetic thing, and no disrespect meant if that is an important issue to you) go and buy a Mighty Mite neck for $100.
Even if you buy the bass new you're still under $500 - I would spend the remaining on a nice set of flatwounds - the previous owner of my bass using rounds has the neck so scuffed up I might have to replace it with a MM one, and to me they both sound and feel better on a fretless.