1995 Corolla. Won't start. Please help!

My car started making noise so my borther and his mechanic friend did a tune up on it, but the check engine light was still on, even though the car was running fine. So they told me to disconnect the battery and if I just needed the tune up the light would go away, so I did just that I dicconnected the battery and the light went away, however I diconnected the battery, and I broke the lead terminal. I was informed that if the alternator was bad to disconnect the battery while the car was running and if it turned off it was the alternator. When we did that after the new lead terminal was changed and the car was running and we disconnected the battery and it kept running. SO we thought that was that and when I got in the car and turned on my lights the car died. When the tow truck got there we told him the same thing, and he jump started my car and again when I turned the lights on it died, so he started it again and disconnected the battery while the car was running and it stayed on and I turned on my lights and it died, so he wasn't sure what it was. Well then he tried connecting the cables, turning on the lights first and then starting the car and that worked, so we ened up driving it home with no problems. So when he parked the car and turned it off he tried to turn it on again and it was dead. So my question is whats the problem, it doesn't start no light not noise nothing, I get nothing. I heard it was the alternator, a wire shortage, the battery, the starter, so I dont know what to do and I obviously can't drive it, and I donnot have a lot of money. What should I do? :Cry: :cry: