How can you offer your work for free to build a portfolio consisting of client work instead of self-initiated projects without degrading your work?

Thank you for the invitation

In the first assessment of the project, there will be a percentage of accumulation in the value of the project, which is the excess percentage of the actual value of the project and be within the portfolio and by which we can achieve free construction without prejudice to work

They are willing to do business within the portfolio without increasing the capital

https://www.webpagefx.com/blog/web-design/6-reasons-why-you-should-do-personal-design-projects/