I learned to play g**tar in 1970, then branched off into slide guitar, banjo (I'm now a recovering banjo player, thank you, haven't touched one in 25 years), and harmonica.
In 1981 I bought a cheapo bass and a little solid-state amp, and put together a group so I could learn to play it. That lasted from July into November, at which time I was recruited into a trio to play lead (g**tar and harmonica -- I've always been better on harp than on anything else

).
Over the next 10+ years the bass player from the trio and I put together various bands, and every now and then he would want to play g**tar so I ended up with bass.
Then I got into recording, and acquired a Carvin LB20 so I could record bass parts. That worked pretty well, and then a lady with whom I had recorded a CD (me on Dobro and bass) recommended me to a guy who was looking for a bass player for a one-time gig as the opening act for a CD release party.
After that I worked on recording for a couple of years until the same guy and I hooked up again and we started gigging as a duo (rhythm g**tar, bass, vocals & drum machine). That worked so well that we recruited a lead player and a live drummer, and we've been going strong, gigging several times a month for local dance halls, ever since.
Along the way I have become a born-again Fender player, and now have a '51 P RI, a '50s P, a fretless J, and, as of yesterday, another P destined to become a fretless.
For the first time I'm a full-time bassist, and it's something I wish I'd gotten into years before.