A side letter for use in a seed financing for an early-stage startup company issuing simple agreements for future equity (SAFEs). The letter agreement includes language for certain rights that are sometimes granted to SAFE investors, such as most favored nation (MFN) rights, rights of first offer (or preemptive rights), "Major Investor" rights, expense reimbursement rights, information rights, and observer rights. This Standard Document has integrated notes with important explanations and drafting and negotiating tips.