yes, you can make enough to support a family. But I wouldnt just quit your job today.. You should make sure you have saved up a safety net worth of income .. maybe 6months worth to give yourself a real chance.. and you can start trading with any amount of money, but depending on your present income, I would begin trading with 5 times what you want to make per month.. that way you just have to grow your capital by 20% per month, which is pretty doable.. and with a 6 month coushion you should be able to have a few bad months without running into trouble.. 

Honestly, i prefer trading without any number to reach.. I just take what the market gives me.. and if i dont make anything today, thats fine by me..