Show HN: I built an app store for open-source financial plans (on spreadsheets)
by mhashemi | 2025-09-15 16:54:42+00:00
Hi HN, Mahmoud here. I'm usually here for Python/FOSS reasons (boltons, glom, CalVer, ZeroVer), and that's still the case, but this time with a twist.

While I was on parental leave from Stripe a couple years back, I started helping my parents figure out their retirement. They're academics coming from overseas, so let's just say I'm a big part of the plan. We found ourselves quibbling over Zoom screenshares, multi-tabbed Google Sheets, and countless links to articles and blog posts. When we looked for professional advice, we found conflicting guidance and misaligned incentives.

I looked at the tools my friends and I use for big decisions and saw a huge gap. This isn't budgeting, nor is this investing. This is actual finance. Money management and decision making. Your options are usually:

1. Read a bunch of Bogleheads, Investopedia, Wikipedia, and Reddit. Then cobble together spreadsheets that we can only hope someone wants to look at (including future you). 2. Hire an expert, which involves a lot of trust, time, and money. You can't shop around too much and you also can't turn back the clock if your advisor burns you. They'll do the spreadsheeting (hopefully correctly) and ignorance is bliss.

I wanted something different. I wanted consumer FP&A, if there were such a thing. A collaborative sandbox for sharing financial context, with a bit of math, plus discussion threads with a context-ful chatbot, and an "explorable explanation" that my parents could use to see how different choices applied directly to them. Google Sheets just wasn't it.

Most importantly it had to solve the trust issue. Most bespoke financial apps are black boxes. I wanted something transparent, verifiable, and forkable. Like open-source software. So, I built FinFam on top of the most broadly-understood low-code platform of all time: the spreadsheet.

FinFam (https://finfam.app) is a platform where you can build and share interactive financial models, powered by XLSX and Google Sheets.

A few examples of questions I've worked through with my early access users:

- https://finfam.app/mahmoud/views/child-cost - How much will it cost you to raise a child from 0 to preschool in the Bay Area?

- https://finfam.app/mahmoud/views/big-tech-vs-startup - Should you take a big tech job or join a startup?

- https://finfam.app/mahmoud/views/ccp-oas-age - When should you start taking your Canadian retirement benefits?

Building each of these models has been super rewarding. The child cost one in particular was a great way to capstone my daughter's 3rd birthday. Yes, I really do have a dataset of her first 2800 diaper changes: https://finfam.app/blog/2025-08-26-baby-cost-view-case-study

Not only has it been more fulfilling and maintainable for me, I'm hopeful that it can open up a new audience of "sheetcoders". There are tons of folks with domain knowledge and spreadsheet know-how, but would never learn (or even vibecode) js/html/react. This way they can build something interactive, without losing the narrative guidance of a good blog post. Get subscribers, find new clients, maybe even get some MRR.

We've been running private alpha all summer. It's still got rough edges, but our small community is getting too much value out of it not to share. Would love to hear what you think. Thanks!