I should try it that way. I literally just started, so I'm trying to find a way to play that suits me just right.
I don't think I could ever do drums. I just don't have the rhythm for it. I am trying to find an affordable set for my husband. Maybe I'll just buy him a piece at a time.
If you don't have rhythm for drums then you might not have rhythm for bass either. Bass is a rhythm instrument, too, believe it or not. The bass follows the drums and the drums follow the bass and make up the rhythm section in which the other instruments follow.
Try following the chord changes on bass in a song and play along to it by ear. That's how I picked up the little bit of bass that I know. The most complex song I can play on bass is Sweet Child O' Mine by Guns N' Roses. And even that's not a super complex song on bass but it's fun to play along to when I get a chance.
As far as buying drums piece by piece, the only drums you can buy separate from the rest are the snare drums. The tom-toms and the bass drum are only sold as a set unfortunately. Most drum manufacturers make entry-level drumsets which are relatively inexpensive, though. I'd hold off on buying a drumset unless your husband is truly committed to learning. Otherwise, the drumset just sits there taking up space. If he's semi-interested in learning, it would be worth your time to look into
practice drumsets. They use rubber pads instead of drums and they take up very little space, hardly make any noise and are reasonably priced. I used one before I got a real drumset.
The cool thing about bass is that you could play it with one finger on the fret board if you wanted to.
E-E-E-E-E-E-E-E-E-E-E-E-E
You mean like that? 
It depends on what you're playing. If you're playing a slower song or a simple walking bassline you can play with 1 or 2 fingers. If you need to riff or play more varied basslines you will need all 4 fingers. Specially if there's no rhythm guitar.
I get exhausted too fast if I try to play drums 
LOL. Drums are a workout, froods. Over time, you start to build up stamina and then you get blisters and callouses all over your fingers, too. Oh, and carrying around all that gear is a pain. I can't tell you how many cymbal stands or drum pedals I've lost or broken while playing shows. Bass and guitar players just gotta worry about their amp (and head if they have one) and their guitar. Vocalists have it the easiest, though. All they have to do is show up lol.
But yeah, bass is also a pretty intricate instrument since it has scales just like guitar. You
can play chords but they end up sounding sludgy IMO. Learning to use four fingers, like you mentioned, is definitely crucial to becoming a somewhat accomplished bass player but for beginners, one or two fingers should be okay just to get started.
