Is it better to develop a web service from scratch or take some product as a basis?

Question

Web development

It is planned to develop a web service where the client fills out a form, entering the necessary data and his email. At the last step, he pays through the robokassa. In the admin panel, these orders are distributed to two or three performers. Well, incrementally, it will be necessary to add functionality that is not included in this mini description.
Question: what is better, to order development from scratch on a framework or to take as a basis some open source system and a minimum of functionality, for example, a Helpdesk system?

Answer 1

Better from scratch - the functionality is not sophisticated, and in view of the planned further improvements in ready-made systems, you will have to complete a bunch of crutches.

Answer 2

Better on a finished system - the functionality is not sophisticated, and in view of the further increase in functionality, most likely half of it will already be in the finished system and everything will slide down to the finished solution anyway.

Answer 3

The framework is used when there is more than 20% of custom functionality from a boxed solution.