OK, so here's the deal... I bought a used mac on Craigslist. It soon began getting bad hacker attacks, and also the previous user had a ton of their personal data on it that I didn't care to have on my computer, so I decided to completely wipe it like new. I am a very advanced PC user, but this is my first ever mac, so I assumed the built in recovery options would work like a windows PC. That was obviously a mistake. I formatted the O.S. and went to install a new system and realized I can't install a new operating system without the original Apple ID from the computer. Only problem is that since it was used when I bought it I don't know what the ID was. I can't go back because I've already deleted the partition and formatted it to prepare for the new installation and now I can't reinstall either.
Would it solve the problem if I create a bootable drive with the O.S. on it rather than installing over the internet, or would it still require an ID that has been used with mavericks before to use?
If so, where could I download a DMG or ISO of the OS?
If not is there any way (preferablly legitimate but I'll take what I can get, hacked methods work too... better than having a paperweight) to install an operating system on my computer?
Would it solve the problem if I create a bootable drive with the O.S. on it rather than installing over the internet, or would it still require an ID that has been used with mavericks before to use?
If so, where could I download a DMG or ISO of the OS?
If not is there any way (preferablly legitimate but I'll take what I can get, hacked methods work too... better than having a paperweight) to install an operating system on my computer?

