Groupon was started as a wordpress blog and while you can always follow the groupon model (i.e. test the market with a simple system), there are scripts available to build your own Groupon site, i.e. daily deal site.
Groupon Clone Using WordPress Plugin
If you are running WordPress, you can build a Groupon clone using a Worpress plugin, Group Buying Site.
The plugin has all the needed functionalities like Deal Creation/Stats/Payment Gateway integration/SEO etc. and pricing starts from $199.
The plugin lets you create deals, launch multiple locations and assign categories/tags to your deal offerings.
What’s really interesting is that you can take the advantage of WordPress’ rich functionality/ existing plugins and make it a much more richer product.
Wroupon
A stand alone product, Wroupon has all that it takes to create a Groupon clone.
Wroupon offers several features like different account views (user view, partner view, admin view), secure remote login, paypal integration, Twitter/Facebook connect etc and costs only $89.
Wroupon or GBS? Well, first get started with selling to brands, get their deals and use either one of the system.
Wroupon seems more scalable than GBS – though the challenge with both is that they only support Paypal [countries like India have banned the local transfer to paypal accounts].
There are other scripts available like Groupscripts, which costs a bomb (in comparison) – $399, as opposed to $89 (Wroupon).