There are some things that might happen, and one of them will happen fairly soon...
1. The engine oil will become so diluted with coolant that it will spin a bearing or seize the oil pump.
2. The coolant will fill a cylinder, and since it cannot compress, if the volume is enough, the engine will hydrolock, and break.
3. The coolant will leak from the headgasket and the engine will overheat, possibly to the point of destruction.
4. The coolant fill in the cylinder will not cause hydrolock, but instead will burn tons of white smoke out the tailpipe. Prepare for police attention should you be doing a James Bond impression.
If you cannot afford another car, you will probably be relegated to mass transit. I'm not being glib. For some time when we were younger, my wife and I could not afford a car. We owned a bus pass. It's cheap, deadly reliable, and not nearly as fun as owning a car, but life is life.
That said, for some years we bought $800 cars and drove them until somthing big broke, then bought another one. Insurance was cheaper 20 years ago, and so was everything else car related. Heck, some days now I think about that bus pass...