AI agency vs. in-house vs. fractional: how to staff your AI work

You've decided AI is worth real investment. Now the harder question: who builds it? There are three honest options, and the right one depends almost entirely on your stage.

Option 1: An AI agency

Agencies start fast and carry broad experience, but you pay for overhead you don't benefit from, and the knowledge often leaves when the engagement ends. They fit a one-off build with a clear spec — a defined feature, shipped and handed over. They're a poor fit when AI is becoming core to your product and you need someone who learns your domain deeply over time.

Option 2: Hire in-house

A full-time AI engineer is the right end state once AI is a core surface and you have enough work to keep them busy. The catch is timing and cost: senior AI talent is expensive and slow to hire, and a single hire takes months to get productive in your codebase. Hiring in-house before you've validated what to build is how teams end up with an expensive person and no shipped feature.

Option 3: A fractional AI lead

The middle path, and usually the right one for SMBs and agencies: someone senior who works part-time as your AI lead — architecting the system, prototyping the riskiest pieces, shipping the first version, and helping you hire in-house when volume justifies it. You get senior judgment without a full-time salary, and the knowledge stays documented in your codebase instead of walking out the door. (For what that role does day to day, see the shape of an AI architect.)

How to choose, by stage

• **Exploring** (nothing shipped yet): start with a short audit plus one fractional engagement. Validate before you hire.
• **One clear build**: an agency or fixed-scope project works — just insist you own the code.
• **AI becoming core, low volume**: a fractional AI lead bridges you until a full-time hire is justified.
• **AI core, high volume**: build in-house, ideally with a fractional lead helping you hire and onboard.

The cost question

Roughly: a fixed-scope build runs a few thousand to low five figures, a fractional lead is $5k–$15k/month part-time, and a senior full-time hire is a six-figure salary plus ramp time. I broke the numbers down in what an AI consultant costs. The cheapest option is rarely the one that ships the right thing fastest.