Can I purchase the single license to use on a development site and then transfer to the new site once live?

Yes absolutely, you can develop the website on your development/test server using the single plugin license.

Then once you go live just log-in to  your account and change the old development website  url  to the new website  url  and the new site will be using that license. Swapping activation keys are handled from your account.

Once the new website is active, you will be able to update your extensions from the WordPress dashboard and get support for it.

If you still see notice messages on your WordPress site

What has happened is that you have added the license keys on your development site and the key is registered to on our licensing server AND the database in your WordPress options tables.

So you need to flush these. 

First remove the license keys from your live WordPress Dashboard > Easy Property Listings > License page.

Deactivate all the keys from your account as shown above.

Re-add the keys to the site you want to activate and press save. That will flush the old and replace it with inside the WordPress database on your site. 

So remove the key and re-add it to flush the old development site URL from the WordPress database.