Job Quote and Invoice App for Electricians and Plumbers

The problem tradespeople have with quoting

An electrician goes to a house, looks at the job and gives a price out loud. The customer forgets what was included, the job grows, and at the end there is an argument about the bill. Payment is often partial: half now, half next week, and the tradesperson keeps that in their head. Quotes lost in conversation are lost income, and so are payments nobody chased.

Independent plumbers, AC technicians, carpenters and painters have the same problem in most countries. They work from a phone, often on a site with poor signal, and they will not open a laptop.

What already exists and the gap

• Jobber: field service software with quotes, scheduling and invoicing; priced per user per month in US dollars, aimed at established firms.
• Tradify: job management for trades businesses in the UK, Australia and New Zealand, priced per user.
• ServiceM8: job-based pricing, with its full app on iOS only.
• Generic invoice apps: invoicing only, no site-side quoting or materials list.

The gap is a phone-first, offline, low-cost tool for a one-person trade business on Android, where the quote is sent through WhatsApp and paid in instalments.

What you build

• Tradesperson: maintains a price list, writes quotes, sends them, marks them accepted, converts to invoice, records payments, keeps job photos.
• Customer: receives a PDF or image on WhatsApp; no app required.

Flows: new customer, quote, share, accept, invoice, payment, history.

The technically interesting part

Speed of quoting. The measurable goal is a complete quote for a common job in under two minutes, standing on site. That drives design: favourites, recent items, templates and number entry that works with one thumb. Time real users and iterate.

Offline data and document rendering. Everything, including PDF generation, must work without signal. Store data in SQLite, render the PDF on the device, and sync later. Handle the case where a quote was edited offline after it was shared: keep versions so the customer's copy and the invoice agree.

For evaluators, show the version history model and the timing results before and after your design changes.

How to evaluate it

• Median time to create a quote for three standard jobs, first version versus final version, with at least 4 tradespeople.
• Number of quotes sent and invoices paid during a two-week field test.
• PDF generation time and app size on a low-end Android phone.
• Offline test: create, edit and share quotes in airplane mode, then sync without data loss.

Suggested plan

1. Weeks 1 to 2: shadow two tradespeople on real jobs, collect common items and prices.
2. Weeks 3 to 6: price list, customers and quote builder with SQLite.
3. Weeks 7 to 9: PDF rendering, WhatsApp sharing, invoice conversion and payments.
4. Weeks 10 to 11: Supabase sync and photo storage.
5. Weeks 12 to 15: field test, timing improvements and report.

Path to a product

Free for a limited number of quotes a month, then a small monthly subscription. Tradespeople pay for tools that clearly bring in money, so show them unpaid invoices recovered. A good first customer is a small team of AC technicians or an electrician who already sends typed quotes. Later, suppliers could pay to have their price lists inside the app.

Scope warning

Do not build scheduling, dispatch or a customer marketplace. Do not build accounting or tax filing. Do not integrate a payment gateway in the core scope.

Learn what you need on Sefism

• Mobile roadmap : React Native and mobile fundamentals.
• Mobile cheat sheet : storage, navigation and sharing patterns.
• Supabase documentation : auth, Postgres and storage for sync.
• Laws of UX : design principles behind a fast quote screen.
• The Mom Test : how to learn from tradespeople without leading them.

Get help with this idea

Keeping this small and fast is the whole challenge. A mentor can help you cut the scope to what your team can finish, choose between the stack options above, and design an evaluation your examiners will respect. You still build it; the help is on decisions, not code.

• Discuss this idea with a mentor
• Send a query to Tauseef
• Book a 1:1 session

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