"Who know what evil lurks in the hearts of men". You bought something off Craigslist and didn't bother to even turn it on before paying for it? Don't blame the Mac. Go to the mirror and write Stupid on your forehead and take a picture of it. Look at that picture before buying from a source with no recourse again. Your Mac could have been used for a boat anchor. That being said, let's see if we can't get you up and running. First we need to know exactly which machine you have.You can either take the battery out and give us the last three figures of your serial number or go here and identify which machine you have: http://www.ifixit.com/Mac-Parts/MacBook-...

We don't even know if the thing has a logic board in it. Let's check and see if it has any RAM. Go here for how to remove the RAM:MacBook Core 2 Duo RAM Replacement Inspect the RAM for corrosion and the correct type. Look at the battery connector and inspect for corrosion. This thing may have had a couple of beers before you got it. Reseat just one stick of RAM at a time and try staring with the battery out an just the AC adapter plugged in. Let us know your findings or any changes in the start up.