Have you made any progress on this? If you want to create static files in the same directory as Blesta (Not advised) you will have to modify the .htaccess file so that it does not redirect those URI's to index.php. Or, you can remove the .htaccess file entirely.
We highly suggest installing Blesta in a subdomain or sub-directory from your main site. So, maybe you have Blesta at /billing/ and then it frees up /contact/, etc for your website.