Having a real business is always important because signature campaign cannot earn you enough to survive so it would always be a side income, but until they are running someone should keep earning through them as well.
Earning from signature campaign should be treated as an additional income and that's not enough to survive you need to find multiple ways to earn more bitcoins.
Depends on your country.
You can easily earn 1btc from multiple signature campaigns. Lots of countries in the world have a monthly wage lower than 200$ on average.
That is right. You can get 1 btc with signature campaign but it would take very long though. Thus, if we depend our daily living and family needs with signature campaign, then it is not wise doing so. It would be good to have some other source of income along with signature campaign that way, you will get some big profits every end of the week or month.
It doesn't take that long for a relatively easy job. It takes me 7 weeks to get a bitcoin. I do some odd jobs here and there that make up about 0.14 btc a week on this forum alone.