For living in China without speaking a word of English.

Any input guys?

Hi!
Here's my take:
I'd say it depends on your circumstances, and what you want to do.
For example if you will be living in a big international city like Shanghai as I am now, you strictly speaking don't need to learn any Chinese characters to get by daily, as lots of things are also in English. For things like filling in forms, if you are coming to work, then your company will help you for your visa/bank card/travel card etc. otherwise get a friend to help.
I think it's more important to just start learning to understand spoken Chinese. In my experience most people are very friendly and helpful here. I wouldn't worry about learning N characters before getting here, just keep learning when you get to China! You'll be seeing Chinese characters daily, so you can learn them as you encounter them.
If you want to quickly learn some characters before you arrive then I'd start with the most useful ones for signs, like entry, exit, man, woman, numbers, telephone, danger, taxi, metro, toilet etc. And use an SRS to memorise them quickly.
Hope that helps!
(I'm assuming you meant without speaking a word of Chinese?)

As far as I have known from my 朋友。 At least, 1000, in order to start dating a Chinese girl

I have to agree with John that most people in China are extremely helpful and in a big city you can move about without any substantial knowledge of Chinese. In the countryside on the other hand you'd need a friend to help you navigate. I wouldn't fixate too much on the characters, rather the words you know. As a ballpark figure the HSK6 level with 5000 words known and 2633 characters should be a good guideline for being able to self-sustain living in China. But as a foreigner it's unlikely you'll end up in the country without a job or student program, so you'd get guidance and help to navigate through everyday life. Just my thoughts on it. Hope it helps you.

As others have said you do not need to know any Characters......speaking of course helps so you need words. But I know people who have spent decades without learning the language and still Iive a comfortable life. People are very helpful and even as your Chinese improves certain situations require specialist vocab which unless specifically pre-learned we just do not experience in daily life. So help is always welcome and usually offered when living in the country.

In terms of hard numbers.....2-3000 characters (Most Frequently used not random characters) is a good minimum.)

First of all, there is no specific total number of Chinese characters. However, to cover daily conversations and readings, mastering around 3000 frequently used characters is rather enough.

You could start with pinyin, which can be thoroughly learned in a few hours, but a working knowledge of Chinese characters takes months. Pinyin also serves the same purpose as the international phonetic symbols used in dictionaries to show how English words are pronounced and is an efficient way of representing Chinese sounds with the Roman alphabet.

Hope this may help.