Web application that will host white-label accounts

Hello, I'm looking to develop an application SAAS/ software for client facing small business in a specific category, that track the progress of their clients. The application will have a few sections, intended to manage and display the progress of the account-holder's clients. This application will be hosted by the main, Master-account and is intended to be licensed out to various account-holders (aka small businesses in a specific category). Each account will be able to use their own version and the data will be collected and shared with the master-account. Master-account hosts all account-holder accounts. In order to become an account-holder, a prospect will sign up to the master-account and create his/her own account. So that the account-holder will be able to use their own account as a white label (without featuring a reference to the master-account in their client facing UI, the master-account’s hosting and domain should be masked by providing the account-holder with a custom URL. The custom URL will need to point back to the account of the account-holder, hosted om the master-account’s hosting solution. The account-holder will be aware that their accounts are hosted by the master-account’s hosting but the account-holder’s users will see only the custom, account-holder’s URL. First stage of development will be the demo for one (Master-account) user. I'm using the words Application or Software. The resulting product can be SAAS or an application or other. When applying please explain your approach, how will it work and how do you intend to get there. Additional details will be available to selected freelancers. To apply, please begin your cover letter with the word Soft, and provide relevant examples of your work. Thanks.