So I’m totally cool with people using the stylesheets we write as a basis for other sites, if it’s the same client using both. However, what’s not so cool? When your new developer needs a) to be explained how to get the original stylesheet; and b)a walkthrough of your styles to understand what I was doing.
If you don’t know how to read source code of a site (both HTML & CSS), you’re not a developer. Don’t sell yourself as one. You’re just going to cause headaches for those of us that are, and who will have to most likely fix what you’ve broken, once you’re finished. And end up costing the client more in the long run.