Creating an invoice, emailing it, and tracking paid/unpaid status is a small, well-bounded build — genuinely one of the more approachable ideas in this set.
Build it
Effort: an eveningRunning cost: $0/mo to start
Why CanICodeThis says Build it
An invoice is a client, a list of line items, and a total — a simple form and a PDF template
Emailing the invoice as a PDF attachment is one transactional-email call
Marking an invoice paid or unpaid is a single status field
The parts that'll cause problems
Accepting online payment directly on the invoice needs a real Stripe Checkout integration
Recurring invoices on a schedule need a background job, not just a due-date field
Multi-currency support, if you need it, adds real complexity around exchange rates
How I'd build this
frontend
Astro or Next.js
database
Turso (SQLite)
email
Resend
hosting
Cloudflare Pages
MVP scope
Create an invoice: client, line items, due date
Generate a PDF and email it to the client
Mark invoices paid or unpaid manually
A dashboard listing all invoices and their status
Postpone to v2
Accept payment online directly from the invoice (Stripe Checkout)
Recurring invoices on a schedule
Multi-currency support
What it actually costs to build
AI agent — with a subscription (Claude Pro/Max, Cursor, etc.)
$0 marginal
AI agent — pay-per-use API, no subscription
$16–$27 one-time
Hosting, once it's running
$0/mo (free tier)
Domain name, if you want your own
~$12/yr
Existing tools solving a similar problem typically run $10–$21/mo — see how they compare below.
The build prompt
Build me a simple invoicing tool, genuinely achievable in a weekend:
1. Create an invoice with client details, line items, and a due date.
2. Generate a PDF (an existing PDF library) and email it to the client via a transactional email API.
3. Track paid/unpaid status manually.
4. A dashboard listing all invoices with filters by status.
Mark-as-paid manually is fine to start. That's a real, complete invoicing tool. Out of scope: accepting payment directly from the invoice via Stripe Checkout, a real, separate payment integration, and recurring invoices on a schedule, which need a scheduled job creating new invoices on a cadence.