Since you're starting from scratch...

Recommend you take a few classes.

One thing that is underestimated, IMHO, is the amount you need to know about cruising boats. There are a lot of moving parts, subsystems. You will be the hotelier during your cruise. You will be responsible for fuel, water, electricity, and refrigeration for everyone, as well as keeping the mechanical systems running. You'll also be the weatherman and doctor. It's very helpful to be mechanically inclined, or take a course focused in this area. It's also helpful to know first aid. If you don't, a class would be good. It's also good to know weather. Again, there are classes.

Once you do a few courses the next step would be a cabin charter on a boat with a captain, and then next you should charter with a captain, ideally with the organization you would do a bareboat charter with the next year.

It all could take 3-4 years doing it part-time in 2-3 week stints per year.

If you have much more free time it could be done in 6-12 months.