APP IDEA: Are you afraid to share source code with external contractors?

Imagine hiring an off-shore contractor to do your HTML and CSS for you. You don't know the contractor so sharing the git repo with source code is out of question.

So the contractor creates the initial version of the HTML and you waste time integrating it yourself and keep integrating the stuff they write while growing your app.

I'm thinking about creating a tool that will make the process much easier by sharing only selected directories of a git repo (e.g. the front-end CSS and HTML) while letting the contractor preview their changes live using a development version of the app under development.

Do you think this tool would be useful?

Would you pay for it?