Feasibility: 5/10

Two problems before we go further.

1. This market is saturated. FreshBooks, Wave, Bonsai, Honeybook, and Invoice Ninja all exist. Wave is free. Bonsai bundles contracts and proposals. You'd be entering a market where the baseline product is free and the premium ones are deeply entrenched. What's your angle that none of them cover?

2. Freelancers are the hardest SaaS audience to monetize. They have low willingness to pay, high churn, and most track invoices in spreadsheets or Notion. The ones who want a real tool already have one.

What would need to be true for this to work: You'd need a specific niche (freelance developers? Designers? Contractors?) with a pain point the existing tools don't solve. "Track invoices" isn't that. "Automatically chase late payments via SMS with legal escalation templates" might be.

What you haven't considered: Customer acquisition cost. How do you reach freelancers who don't know they need this? SEO against FreshBooks is a 3-year play minimum.

Before scaffolding anything, answer this: have you talked to 10 freelancers who actively hate their current invoicing tool? If not, that's step one.