I have an Excel / Google Sheets file that allows users to input their business numbers (vehicles, equipment, overhead expenses, employees, etc), and their costs to be able to create a budget and then to create an estimate from these materials using some formulas that draws from these business numbers. The user should be able to edit their budget with their information and then save estimates for their clients drawing from their business numbers (for example, they have 1000 hours in a year and the project takes 100 hours it will take 10% of their overhead costs, they can add employees to the project, and they can then add their materials to the estimate).

It is 10 tabs that allow users to choose from a dropdown item, that item prefills the cost of that item, and they can input their quantity for it to provide them with a price. They can continue this with their material cost, overhead expenses, and profitability. Users should be able to create their own items, input the value for those items, and allow them to then choose those items from a dropdown after they have been added to the database.

I am looking for somebody to build me a software from this file. It will be web-based and users will pay monthly to join. I would preferably like somebody to build it and remain close with us as an ongoing freelancer.

What programming language would you use?
How long would this take?

See photos for more from this spreadsheet.