You have outlined the only "pro" for using your production environment for development: It requires minimal setup time. The "cons" however are numerous.
Generally speaking your development and testing environment should be entirely separate from your live production environment -- If your dev code has a bug that spews junk all over the production server's filesystem, or worse starts deleting stuff from your production database, you will be in for a world of hurt trying to undo the damage.
A proper development environment also allows you to test things you'd never try to do in production (deleting scads of data for example) to see how the system behaves.
VMWare is cheap (in fact their free tools are great for setting up development environments), and decent hardware to run it on isn't that expensive. Alternatively you can pursue other (workstation) virtualization solutions like VirtualBox for setting up a development environment.