There is a predictable sequence to building a finance function, and the most common misstep is hiring the most senior person first.
A full-time CFO at $200,000 to $300,000 is usually the wrong first hire for a Series A company. The work at that stage is closer to clean books, a reliable close, and a defensible model than to capital-markets strategy, so the better early hire is often a commercially-minded Head of Finance, with a full-time CFO arriving later, around $15 to $25M in revenue. Useful trigger points for outside help: roughly 20 paying customers, $200K or more in monthly burn, or a seed round closed.
Fractional support runs $5,000 to $15,000 a month against $300,000 to $450,000 a year for a full-time hire, and startups that use it tend to close their rounds about nine months faster.