It sounds totally fake. Bass sound is not just the sound of a 6-string guitar dropped down an octave lower. Bass is a completely different tonal quality.
The way you play bass is also very different stylistically.
I would recommend buy a used bass for $200 or under and get used to playing that, if you are serious about recording and want to play all the parts yourself that is the way to go.
I play old school because I am old school.