time req to learn bass guitar if i know how to play an acoustic guitar

i have been playing the acoustic for about 2 years now..
i am buying a bass guitar, i just wanted to know how long it will be before i start playing good bass lines ..
(i practice about 10 hrs a week)

depends
you said you "know" acoustic
what does that mean
i mean
are you really good with a pick
or finger picking
or slap techniques
or strumming
or leads
or improvisation
do you practice wth a metronome?
it depends how good you really are
starting bass is easy...progressing in it is harder
assuming that you are decent at acoustic guitar and you practice ten hours a week i would say you could easily start playing simple bass riffs
in a week and become pretty proficient in about six-eight weeks