Best workflow for adding store to existing website

Hi there,

I have a client who would like me to add a store to their existing website. Just wondering what the best workflow for this would be.

• Turning the site to private for the period of the build and using an under-construction type of page in the interim.

• Duplicating the site, doing the work on the duplicated site, then replacing the original site with the duplicated one by changing the domain over to the new version of the site. Assuming this will affect their SEO etc?

I'm thinking that turning the site to private for a period will be the simplest way? Is there a best practice workflow for this type of situation?

Thanks in advance,

Jess