Can you teach me to sing?
How long will it take before I sound any good?

Difficult to answer these sorts of questions.

Depends what ‘sing’ means to you.

To some people, “If it ain't as good as Barbra Streisand / Pavarotti (whoever) – it’s absolutely awful!”
Meaning they have a very high expectation of what 'sing' means to them.

Others, if they can sing AT ALL and it is vaguely recognisable as a tune,
they are as happy as they can be!
So the answer to these questions all depend on your personal expectations.

How quickly it happens is also a personal thing.

This depends on how much time you have to give to it, what type of music you want to sing,
and your aptitude for learning in general. -- (not easy to tell when you start!)
Previous musical experience MAY be a factor too. (but not as much as people tend to assume!)

So all I can usually 'guarantee’ is that I can make you sound better than you do now!
Some improvement is usually pretty immediate..

I can give you a better idea after we have a session and I hear where you are now.