Help! Heater Core leak.?

I think my heater core is leaking. It has a sweet smell and when I turn on the defrost there's a green fog that comes out from the vent (this is only when the defrost is on). I can't afford to get it fixed right now cause they said it's going to be close to $1,000 and I don't have that kind of money. I've been smelling the smell for the past month. Does it affect my health when I inhale it? And, do you know if I can find a cheaper solution or if you know of any places that fixes it for cheap? Oh, and what would happen if I keep driving it unfixed, will my car break down? I don't turn the a/c or heater on cause the smell is too strong when I do that and even when it's off, I smell it a little.