My first advice to anyone wishing to take up the double bass is the same as Mr. Punch’s advice to those about to get married: Don’t! But there are reservations.
First, I was happily married to my late wife for over fifty years. Second, if you do decide to do it, make it a wholehearted attempt. The bass is one of the most difficult instruments, so recognize that it will be a challenge, and then, even if people tell you that music is a precarious profession, but you are still eager and anxious to make it a career then go for it full steam. I was always warned never to be a musician, but I disregarded all well meaning advice and did very well
There are many things you will have to think about; tuition, an instrument, finance and eventually job hunting and auditioning etc. so I propose to write a few posts giving you the benefit of my 70 years on the bass, and if you budding young bass players seem to want my advice then I shall continue.