I have just installed Oddyutza's awesome Billing and Automated invoice system but i felt that the installation instructions where not concise enough, i have posted the steps i used in case anyone is struggling.
# cd /usr/local/src
# mkdir billing
# cd billing
# wget 
http://www.omegabill.org/releases/OmegaB...Build4.zip
# unzip 
OmegaBill_v1.0_Build4.zip
# mkdir /var/www/ispcp/gui/tools/billing
# cp -r 
OmegaBill_v1.0_Build4/* /var/www/ispcp/gui/tools/billing
# chown -R vu2000:www-data /var/www/ispcp/gui/tools/billing
# cd /var/www/ispcp/gui/tools/billing/includes
# pico configuration.php
Change
// MySQL database configuration:
$server = "localhost";
$user = "billing";
$password = "
mypass";
$dbname = "ispcp_billing";
$installpath = "
http://billing.domain.tld/";
# cd ../
# cd \#SQL\ FILE/
# mysql -u root -p
CREATE DATABASE 
omegabilling DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;
GRANT ALL PRIVILEGES ON ispcp_billing.* TO billing@localhost IDENTIFIED BY '
mypass';
quit
#mysql -u billing -p 
omegabilling < ispcp_billing.sql
# cd ../
# cd \#CRON\ FILE/
# pico cron_billing.php
Change
#ispCP config
$ispCP_host = "localhost";
$ispCP_user = "
ispcp username";
$ispCP_pass = "
ispcp pass";
$ispCP_db   = "ispcp";
#Billing config
$Billing_host   = "localhost";
$Billing_user   = "billing";
$Billing_pass   = "
mypass";
$Billing_db     = "ispcp_billing";
#php -q cron_billing.php
#pico /etc/apache2/sites-available/00_master.conf
Alias /billing /var/www/ispcp/gui/tools/billing/
#pico /etc/apache2/sites-available/07-billing
<VirtualHost XXX.XXX.XXX.XXX:80>
    ServerAdmin     webmaster@yourdomain.tld
    DocumentRoot    /var/www/ispcp/gui/tools/billing
    ServerName      billing.yourdomain.tld
    ServerAlias     billing.*
    ErrorLog        /var/log/apache2/users/billing-error.log
    TransferLog     /var/log/apache2/users/billing-access.log
    CustomLog       /var/log/apache2/billing-traf.log traff
    CustomLog       /var/log/apache2/billing-combined.log combined
    <IfModule suexec_module>
           SuexecUserGroup vu2000 vu2000
    </IfModule>
    <Directory /var/www/ispcp/gui/tools/billing>
        Options -Indexes Includes FollowSymLinks MultiViews
        AllowOverride None
        Order allow,deny
        Allow from all
    </Directory>
    <IfModule mod_fcgid.c>
        <Directory /var/www/ispcp/gui/tools/billing>
            FCGIWrapper /var/www/fcgi/master/php5-fcgi-starter .php
            Options +ExecCGI
        </Directory>
        <Directory "/var/www/fcgi/master">
            AllowOverride None
            Options +ExecCGI MultiViews -Indexes
            Order allow,deny
            Allow from all
        </Directory>
    </IfModule>
    <IfModule mod_fastcgi.c>
        ScriptAlias /php5/ /var/www/fcgi/master/
        <Directory "/var/www/fcgi/master">
            AllowOverride None
            Options +ExecCGI MultiViews -Indexes
            Order allow,deny
            Allow from all
        </Directory>
    </IfModule>
    <IfModule mod_php5.c>
        <Directory /var/www/ispcp/gui/tools/billing>
            php_admin_value open_basedir "/var/www/ispcp/gui/tools/billing/:/etc/ispcp/:/var/run/ispcp.lock:/proc/:/bin/df:/bin/mount:/var/log/rkhunter.log:/var/log/chkrootkit.log:/usr/share/php/"
            php_admin_value session.save_path "/var/www/ispcp/gui/phptmp/"
            php_admin_value upload_tmp_dir "/var/www/ispcp/gui/phptmp/"
        </Directory>
    </IfModule>
</VirtualHost>
# a2ensite 07-billing
# /etc/init.d/apache2 reload
Goto 
http://billing.yourdomain.tld
Username: admin
Password: 
omegabill
when using php -q cron_billing.php to add the cron job i can only seem to get it working using "root" as the ispcp admin user