Coach House can help you start fundraising even pre-501c3:

Coach House fiscally sponsors community-based, civic, and mission-driven projects that are charitable in nature, primarily noncommercial, and aligned with a clear public benefit.

Our fiscal sponsorship program is structured as a grantor–grantee relationship, sometimes referred to by the IRS as a Model C fiscal sponsorship.

The Model: 

Coach House serves as the fiscal sponsor (the grantor)
Your project or organization serves as the sponsored entity (the grantee)

Donors, foundations, corporations, or public entities make charitable contributions to Coach House for the benefit of your approved project. Coach House then makes charitable grants to you to support project-related expenses.

This structure allows projects without their own 501(c)(3) status to:

Receive tax-deductible donations
Apply for many grants
Establish financial credibility
Operate with appropriate oversight and compliance