Hi,
Hope this finds you well; I am Adnan and before you go through from the whole proposal, first thing first. I am eager to set up an infrastructure for your sending, but, I regret that dealing in terms of sharing profit is out of my scope currently. We are basically an email infrastructure provider, we can help you configure mail server with an appropriate set of software resource and configuration measures for sustainable email delivery.
Sending them in smaller volumes is the right idea but your thought of using Gmail won't work for mass mailout, as Gmail may not let you send 100-150 or 500 emails depending on how you are using it. The better solution for doing this is opting for a self-hosted email infrastructure. It may not cost you as heavily as I had to quote due to the project budget you have allocated. I quote you $300 for a good email infrastructure, set up on Linux CentOS platform configured with commercial MTA application PowerMTA and will be using IEM or Mumara, preferably to compose, schedule and track the sent emails.
Let me know if this is something you are open to deal with too, we can discuss further.
Regards,