It all starts with creating an MVP webapp first, once you have done that you can add things you want like management, purchasing, invoicing, etc.
Minimum Viable Product is that version of a new product which allows a team to collect the maximum amount of validated learning about customers with the least effort. MVP is a process of building a new product with core functionalities and important, minimum features, to test how the target audience would respond. Then, the building of the actual product takes place with the full set of features after a series of iterations, with feedback from early adopters. MVP helps in testing, designing, and delivering the final product. Several businesses have pitfalls while trying to launch a Minimum Viable Product for a mobile app or a web. The purpose to build an MVP is to launch a product quickly, based on your idea, with a small budget. This approach allows you to collect users’ feedback for the primary product and include it in future iterations.
You can read more here: https://www.netsolutions.com/insights/how-to-build-an-mvp-minimum-viable-product-a-step-by-step-guide/
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath