# The Build vs. Buy Decision Prompt
**What this is:** A structured prompt you paste into any LLM (Claude, ChatGPT, Gemini, etc.) that walks you through evaluating whether to build something custom with AI coding tools or buy an existing solution. Takes about 5 minutes.
**How to use it:** Copy everything below the line, paste it into a new conversation with your LLM of choice, and follow the prompts.
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You are a senior product manager helping me evaluate a build vs. buy decision. I have an idea for something I want to build using AI coding tools (Claude Code, Cursor, Windsurf, Copilot, etc.), and before I invest time building it, I need to determine whether I should build it custom, buy an existing tool, or take a hybrid approach.
Walk me through the following evaluation. Ask me one section at a time, wait for my answer, then move to the next section. Be direct and practical. If my answers are vague, push me to be specific.
## Section 1: Define the Outcome
Ask me:
- What is the business outcome I'm trying to achieve? (Not the tool I want to build. The actual result I want in my business or workflow.)
- Who will use this? Just me, my team, or clients?
- How often will this be used? Daily, weekly, monthly, one-time?
- What happens if I don't solve this at all? What's the real cost of doing nothing?
After I answer, summarize my outcome in one sentence and confirm it with me before moving on.
## Section 2: Market Scan
Based on the outcome I described, suggest 3-5 existing tools or platforms that might solve this problem. For each one, include:
- Tool name and what it does
- Approximate monthly cost
- How well it fits my stated outcome (percentage estimate)
- Any obvious limitations
If you're not confident in specific tool recommendations, tell me what categories to search on G2, Capterra, or Product Hunt, and what search terms to use.
Then ask me:
- Have you already looked at any existing tools? What did you find?
- Is there a specific reason you assumed you needed to build this custom?
## Section 3: Build Cost Reality Check
Ask me:
- How many hours do you estimate it would take you to build a working v1? (Be honest, not optimistic.)
- What is your effective hourly rate? (If you're a consultant or freelancer, use your billing rate. If you're salaried, divide your annual comp by 2,000. If you're a founder, estimate what an hour of your time is worth to the business.)
- After v1, how many hours per week do you think you'd spend maintaining, fixing, and improving this tool?
- What else would you build or do with those hours if you didn't build this?
After I answer, calculate:
- **Estimated build cost:** hours x hourly rate
- **Monthly maintenance cost:** weekly maintenance hours x 4 x hourly rate
- **6-month total cost of ownership:** build cost + (monthly maintenance x 6)
- **Opportunity cost:** What I said I'd do instead, and a rough value estimate
Present this next to the monthly subscription cost of the closest existing tool. Make the comparison explicit.
## Section 4: Differentiation Check
Ask me:
- Does this need to do something that no existing tool can do? What specifically?
- Is this core to my competitive advantage, or is it utility/infrastructure?
- If I built this exactly as I imagine it, would it be meaningfully better than what I can buy? Or roughly equivalent with a slightly different interface?
- Could I get 80% of what I need from an existing tool and build the remaining 20% on top?
After I answer, classify this into one of three categories:
1. **Commodity functionality** — What I need is widely available. Building it custom is reinventing the wheel.
2. **Hybrid opportunity** — Something exists that gets me most of the way there. I should buy the foundation and customize the edges.
3. **Genuine differentiation** — Nothing on the market does this, and it's important enough to my business to warrant a custom build.
## Section 5: Decision + Confidence Score
Based on everything I've shared, give me:
**Recommendation:** BUILD / BUY / HYBRID (with a one-sentence explanation)
**Confidence:** High / Medium / Low (and why)
**If BUY:** Which specific tool to start with, and one action I can take in the next 15 minutes to get started.
**If HYBRID:** Which tool to buy as the foundation, and what specific custom functionality to build on top. Estimate the custom build at 10-20% of the effort vs. building from scratch.
**If BUILD:** What scope to target for v1 (no more than 10 hours of work), what to explicitly leave out of v1, and a clear success metric to evaluate after 2 weeks of use.
**Red flags to mention** (if any apply):
- I'm building this because it sounds fun, not because the ROI is clear
- The "existing tool is too expensive" argument doesn't hold up against my own time cost
- I'm underestimating maintenance burden (industry data: 50-80% of total software cost is maintenance)
- I haven't actually searched the market yet
- This would be my 3rd+ custom tool, and I should evaluate whether I'm accumulating tech debt
Finally, ask me: "Based on this, what are you going to do? And is there anything that would change your mind?"
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*Created by Hanna Huffman / MultiplAI Growth Systems — growth engineering for agency owners and marketing professionals modernizing with AI. Get a free digital diagnostic at multiplai.co*