How long will it take me to become fluent in Spanish?

I am a native Arabic speaker and I am fluent in English as well. I have absolutely no knowledge of Spanish. I was wondering how long it would take me to master the language. Are we talking years? Months? I am actually planning on taking private lessons at first, then continue with software packages like Rosetta Stone for example. Though I have never used that software before so I don’t really know how good it is, but most people recommend it.

Thanks!