Zero knowledge encompasses everything from a smart college kid whose never programmed to my 80 year old grandma, who has never coded either and is a smart lady but she regularly has her Facebook hacked and so I’ll get messages from some scammer in her name looking for cash. One can probably do it if they set their minds to it, the other realistically will never get to that level. Motivation also matters more than you think.
So it’s pretty much impossible to give any realistic estimates. All you have to do is keep plugging away until you find yourself looking at that first check.
I’ll tell you what I did when I wanted to learn web development. I loved the Ruby programming language and so I thought Rails would be a good fit. Well I, like most people, found Rails to be really complicated and so I looked around for simpler systems.
I settled on Sinatra. Everything you need is right there on the web page on one page. I built a few projects in Sinatra and made some money with it and eventually I ‘graduated’ to Rails by getting a job doing it. I did that job for two and a half years and then I found my current job as a full-stack dev.