Website business directory flutter web and mobile app

"Kindly review the documents for details on the requirements. Please provide the fixed price, estimated duration, and the possibility of implementing this as a SaaS. The objective is to enable individuals interested in establishing a website directory to create one with its own database. Users should have the option to utilize a subdomain or their own domain without access to the code. Additionally, I should have control over all site owners, with the ability to toggle features as needed. The hierarchy is Admin -> Site Owner -> Store -> Customer."