Should my first engineering hires be senior or can I start with mid or junior developers?

In the first year of a product, your main risk is slowly building the wrong thing, not overpaying for experience. One or two strong seniors can design the architecture, make sensible trade-offs, and avoid mistakes that lead to rewrites. Juniors and mids are valuable once there is a stable base and someone to mentor them, review their work, and shield them from chaotic priorities. If the budget is tight, consider one senior and one mid instead of several juniors; fewer people making better decisions can often deliver more than a larger, inexperienced team. Look for individuals who have shipped in messy real-world conditions, not just those with impressive titles.