The first step is to believe you can. Practice everyday. That goes for anything. If you are really dedicated and believe in yourself then who knows how far you'll take it! Take classes, practice, get as much info as you can. Something that helps me is telling other people I'm going to do it, because you don't want to look like a liar so you kind of have to go through with it then.
I guarantee you're not a bad singer. Start telling yourself you're good. I also find that when I do that I improve.
it totally depends. Like if the person didn't have an ear for music and is super off key then I don't think so because there isn't really any fixing that problem. However if they have an ok voice, and just aren't trained, maybe they could if they started voice lessons right away.
I was in choir for about 7 years. It would take a lot of training and a lot of dedication. But another factor is finding something that works well with/for your voice, and some voices just aren't made for singing, or certain songs and such. I would work with someone who has more experience/training in it, like a friend or family member if that's an option, and get tips or advice from them, as well. While it can take a while to learn and train your voice, I don't know about that being impossible.
I think it depends on a whole lot of stuff.
-How much time are you willing to put into it?
-How much money are you willing to put into it?
-Are you gonna give up if you don't do well right away?
It depends on a lot of things...like, how often you will actually train, how good you already are with your singing voice and music theory, your diet...apparently(?), among other things.
Thanks for the comment
you mean like the try-outs for American Idol ?