Folder with a question mark on purchased Mac I just got my MacBook Pro mid 2012 laptop and stupid me did something to it, now I have a flashing folder with a question mark. The previous owner said she accidentally deleted the software when she was transferring her things to the other laptop. 

I rang AppleCare and I did all these things to try and solve it but all it come up with is a password but I don't know the password. Is this a common thing? Should I take it to Apple Store?

Not in contact with the seller.
Folder with the question mark usually means "no valid device to boot from".

Try to boot to recovery (if any exists) by keeping pressing command + r when turning on the Mac. You should be able to reinstall it there.

If still fails you may try Mac OS X internet recovery (cmd+option+r keeps pressed while pressing power button)

If still fails, get someone with a working Mac with App store to get you a Mac OS X El Capitan Installer following the steps listed here:
https://support.apple.com/en-gb/HT201372

Make sure the usb disk itself is a bootable instance (as in some cases it is blocked by hardware design).

When the bootable USB disk is plugged in, hold down the option when turning on to get a selectable boot device list and you should be able to see a disk to install to (if, not there is not any, it will be a hardware issue then -> go to Apple store or get someone else to fix).

After in recovery mode if seeing a disc to install to: feel free to erase the disk as Mac OS Extended (Journaled) (==HFS+) and install your instance with your Apple ID.