UI development for file sharing, social network, and encrypted messaging service en Barcelona o en remoto

I am looking for someone to help with the frontend development. We are actually developing a Google Drive like service but using exclusively Javascript and Electron. The service also includes a social network and an encrypted messaging service. All that requires UI improvement.

Please consider that we are only going to use Javascript, jQuery and CSS. No AngilarJS or any other framework as it would require to rebuild all the code.

IMPORTANT:
Not interested on outsourcing companies. Please do not contact me if you are not independent.
I offer the possibility to be mostly retributed based on the company's brute incomes (which are publicly available by law). We would sign a contract and you would be co-owner of the code you develop and will be retributed in perpetuity based on the incomes that the company gets and the valuation of your contribution. I can also pay a minimal wage if required, but unfortunately not a SV-like wage. So, the final wage has no upper limit.
If your work is sustained in time and you are interested, we could then negotiate equity for you.
I can give you further explanations if you contact me.