I am guessing that you at least have some kind of ear for music and that you are not tone deaf...
I would suggest you go to a vocal trainer and get someonet to help you with identifying the areas where your voice needs improving. Then put together a training program that will allow you to build on the areas that you need work on.
Singing the whole day will improve your vocals but it might also damage your vocal chords if you apply them wrong. This is why I suggest a vocal trainer, since you appear to want to make a living from music.
Always remeber, if you have to strain yourself to get to a note something is not right...
IMHO