simple restfull api in .net 4.6.1

I am looking for a web api that will be built in .net4.6.1. the web api has to be restfull. it will have 3 parts. the first is the frontend. the frontend should be build in html css and java script(i prefer angular js with ui-router for routing). it should be totally independent from the backend. (i mean no middleware. it should be a client that consume a unknown web API). second part is the backend. the backend should be a asp.net core web application web API. it should have controllers, properties, and models. (you can others as needed) controllers have only 1 job receives and return only json to the client. Others task should be handle by properties. models store data to the database and each entity should be a stand alone model. the last part is a database. I prefer it to be a SQL database. something that can be access by another program. the web API has: companies, Users, Products, Invoice, Receipt. a user belong to a companies. a user has a login but companies does not. a user of a companies can an invoice to another companies. this invoice will be seen by only users of the sending companies and reviving companies. an invoice has a list of product. once the invoice is accepted a receipt will be generated and sent back to the companies that sent the invoice. each companies has a list of product. but as product a really common i prefer to have one list and have them share it. but users can only see or edit the product they have in stock. so to summarize, the companies has users and product. a user can only change product they have, (add, remove) the user can buy(write an invoice to another company) or sell (accept and invoice from another company and return the receipt). see the history of his activities. on the frontend the user will have a login page. once login he will have a home page. the home page should give him link to his profile, his invoice(these are invoice that his companies sent to other companies), his command(this are the invoice other companies sent their companies), his receipt (sent and received as well ), and the inventory(product list this is the product they have in stock). the profile page should give him the way to edit his profile and change password. the invoice and command page should give list of invoice and a way to modify them. the receipt page should give a list of receipt and a way to view it. and lastly the inventory once you click on product it should give you detail and a way of changing it. it should also have a search bar where you can type a name and brings you all the product that match this name. remember this is an eCommerce. so it should have a way to search a product. this search will return all the product and companies that has it just as a normal eCommerce site. this is a prototype that i m building. i will give 3 people the project and compare the result to choose the one that will build the actual website. u can use any product since it is for demos. i will pay for the demos but i need them done faster.