No you do not need to buy it but you do need to download the install files from Apple and SAVE them. Then you can create a a DVD or USB thumb drive of the install files.
Try this link for the method that has worked for me to get those files and save them then create the USB drive.
Use LionDiskMaker 1.7b to create the USB drive. Works real well.
I need to create a bootable Lion DVD or USB flash drive so that I can repair my internal drive.
This statement confuses me. You don't need anything to repair your internal drive. Just hold down cmd-r on restart and boot into the recovery HD. Are you aware of the Recovery HD? http://support.apple.com/kb/HT4718
Now, if you want something to boot from if yiou ever need to swap drives, you can try any one of the noted options. Even then, your Mac should be able to boot into the Internet Recovery without a bootable drive at all. That does require good internet access, but is another option.
Asside from all that, a clone would be a good option (as already mentioned) to have if you don't want to be saddled with downloading Lion again to reinstall.