Great way to promote via email

I am offering services of web design and marketing.

One strategy I intend to try out is this:

I will create only a home page for a website of a particular business type. This will be for a site-preview purpose only.

I will make it look really attractive and impressive.

It would include generic photos and some text for the particular business branch.

The site is built in WordPress, btw.

Then I will select 10 companies from that branch and find their email contact info.

And then I will email them all at once with my offer!

Now comes the part where I need your help!

Im sure that by now you see what I am aiming at - sparking an interest and perhaps even getting a better price for my services.

I would allow an open bidding for that website.

I need your help to create the best way for this to function.

I will be using Gmail.

How could I best organize this way of promotion? How do I enable them to see the preview of my site - should I just give a direct link to the wordpress where it is being created or something else?

How should the bidding go - should they simply give a bid in their reply?

I think this is a great way to promote and I am obviously willing to share the idea, just help me out with some tricks of refinement.

Regards,

Wolf