A bit over a year ago, I was a completely monolingual English speaker with zero experience with the French language. Twelve months later, I very comfortably passed the internationally recognized DELF B2 exam. If you don’t know what “B2” means, check out the CEFR scale.
Furthermore, all of my progress was the result of study and practice at home. My learning was entirely self-directed, without any formal programs or immersion. This was only possible through the many amazing resources available online, many of which are free. Furthermore, I succeeded in part because I prioritized receiving quality input and producing output, particularly by spending lots of time talking with fluent French speakers.
I will say my learning pace was somewhat aggressive, in that I devoted a lot of time towards learning French over the past year, but it was nowhere near full-time study.
I wouldn’t call myself completely “fluent”, but to give you an idea of my level, here are some things I can do without much trouble: