2005 Mazda6 NOT RUNNING
 

I just recently bought a 2005 Mazda6 to fix up for my son to drive. Bought the car knowing that it did not run and not sure what the problem was exactly. So heres how it sits. The car has just under 100k. When I put the key in to start the car, very little happens. The dash lights up, infact the dash is the only thing that works completely. So, besides the dash, one window works, the right headlight works and the horn. But nothing else. The previous owner says he has replaced the window switches. So I checked the battery, full charge. I checked every last fuse and none of them are blown. I have cleaned and fixed a few grounds that were questionable. Still nothing. I am thinking its the ECU but I dont want to spend $250 on it if theres some other explanation. Any ideas?

Also i have plugged my scanner in and nothing, acts as if it is not connected to anything.