There are free systems out there. If you have no budget, and want to get started, download one of these:
- Subversion: http://subversion.tigris.org
There are good ones to pay for as well, and some of them have other features and integration you may like:
- Team Foundation Server – http://msdn.microsoft.com/en-us/vstudio/ff637362.aspx
- Vault – http://sourcegear.com/vault/
- Perforce – http://www.perforce.com/product/components/perforce-versioning-engine
There are ways to do this, but please pick one. Version control is a must for professional software developers. That means if you write code, and get paid for it, use version control. If you write code, and don’t get paid for it, value your time and use VCS anyway.