What forms do I file after I obtain 501c3 status?
First, think about state tax-exempt status. It is generally not difficult. Here is a link that may help you: https://501c3go.com/about-501c3/state-tax-exempt-status/
If you bring in less than $50,000 in a year, you file the 990-N, which is a simple Internet filing with the IRS, no financials. Five minutes. If over $50,000 your CPA will prepare and file the form 990 for you. There is no IRS fee to file.
Most states have annual filing with a small filing fee.