I am getting the following error when trying to launch my app in the sandbox:

JInstaller: :Install: Error SQL DB function failed with error number 1060
Duplicate column name 'address' SQL=CREATE TABLE IF NOT EXISTS `[PREFIX]demo6003_employees` ( `id` int(11) NOT NULL auto_increment, `params` text NOT NULL DEFAULT '', `picture` VARCHAR(255) , `first_name` VARCHAR(25) NOT NULL , `last_name` VARCHAR(25) NOT NULL , `address` VARCHAR(30) , `address` VARCHAR(30) , `city` VARCHAR(25) , `state` VARCHAR(2) DEFAULT 'TX' , `zip` VARCHAR(10) , `date_started` DATE , `home_phone` VARCHAR(255) , `mobile_phone` VARCHAR(255) , `email_address` VARCHAR(255) , `active` TINYINT DEFAULT 1 , `notes` TEXT , `attachments` VARCHAR(255) , `employee_fk` INT(11) , PRIMARY KEY (`id`) );
SQL =

CREATE TABLE IF NOT EXISTS `#__demo6003_employees` (
`id` int(11) NOT NULL auto_increment,
`params` text NOT NULL DEFAULT '',
`picture` VARCHAR(255) ,
`first_name` VARCHAR(25) NOT NULL ,
`last_name` VARCHAR(25) NOT NULL ,
`address` VARCHAR(30) ,
`address` VARCHAR(30) ,
`city` VARCHAR(25) ,
`state` VARCHAR(2) DEFAULT 'TX' ,
`zip` VARCHAR(10) ,
`date_started` DATE ,
`home_phone` VARCHAR(255) ,
`mobile_phone` VARCHAR(255) ,
`email_address` VARCHAR(255) ,
`active` TINYINT DEFAULT 1 ,
`notes` TEXT ,
`attachments` VARCHAR(255) ,
`employee_fk` INT(11) ,

PRIMARY KEY (`id`)
);

Component Install: SQL error file DB function failed with error number 1060
Duplicate column name 'address' SQL=CREATE TABLE IF NOT EXISTS `[PREFIX]demo6003_employees` ( `id` int(11) NOT NULL auto_increment, `params` text NOT NULL DEFAULT '', `picture` VARCHAR(255) , `first_name` VARCHAR(25) NOT NULL , `last_name` VARCHAR(25) NOT NULL , `address` VARCHAR(30) , `address` VARCHAR(30) , `city` VARCHAR(25) , `state` VARCHAR(2) DEFAULT 'TX' , `zip` VARCHAR(10) , `date_started` DATE , `home_phone` VARCHAR(255) , `mobile_phone` VARCHAR(255) , `email_address` VARCHAR(255) , `active` TINYINT DEFAULT 1 , `notes` TEXT , `attachments` VARCHAR(255) , `employee_fk` INT(11) , PRIMARY KEY (`id`) );
SQL =

CREATE TABLE IF NOT EXISTS `#__demo6003_employees` (
`id` int(11) NOT NULL auto_increment,
`params` text NOT NULL DEFAULT '',
`picture` VARCHAR(255) ,
`first_name` VARCHAR(25) NOT NULL ,
`last_name` VARCHAR(25) NOT NULL ,
`address` VARCHAR(30) ,
`address` VARCHAR(30) ,
`city` VARCHAR(25) ,
`state` VARCHAR(2) DEFAULT 'TX' ,
`zip` VARCHAR(10) ,
`date_started` DATE ,
`home_phone` VARCHAR(255) ,
`mobile_phone` VARCHAR(255) ,
`email_address` VARCHAR(255) ,
`active` TINYINT DEFAULT 1 ,
`notes` TEXT ,
`attachments` VARCHAR(255) ,
`employee_fk` INT(11) ,

PRIMARY KEY (`id`)
);

There was an error installing the package

I think you have 2 fields in your employees table called address according to your error "... `address` VARCHAR(30) , ..."

Thanks again!

Don't forget about profile plugin, native joomla plugin that allows to extend the user infos.
www.inmotionhosting.com/support/edu/joom...profile/view-profile
It has been requested that cook integrates this one.
www.j-cook.pro/forum/12-new-functionalit...-profile-plugin#3790
Or you can go further with this :
docs.joomla.org/Creating_a_profile_plugin