[brudgers]

Do you want to work for the company asking for the changes? Because you have one potential customer. One prospect. And from what I see in the question, they haven't offered you a large pile of money to make the changes. The question reads they have asked you to work for free.

Where are you at in all this? Are you already a contractor with existing processes, relationships, and infrastructure for negotiating contracts, getting paid, and supporting large companies? Have you already paid the dumb tax beginning contractors pay for things learned the hard way?

How much money do you need to support the project long term? Does the person who asked for changes have a budget and the discretion to pay you? Good luck.