I built a free iOS app to answer one question: How do children fit into your financial future?
A few months ago I started wondering how having children would actually affect my long-term financial picture — not in a vague "kids are expensive" way, but concretely. How much would childcare cost in my area? What would college do to my savings rate? How many years would it push back financial independence?
I couldn't find a tool that answered those questions in one place, so I built one.
What FinSim does
FinSim is a free iOS financial simulator that runs two scenarios side by side — your wealth trajectory with children and without — so the trade-off is immediately visible rather than something you have to calculate yourself.
It models:
Child costs using real NDCP childcare data by county (3,200+ US counties)
Per-child birth age control so costs kick in at the right point
Debt payoff timeline and its effect on long-term wealth
Retirement drawdown based on the 4% rule
Financial independence age and how each decision shifts it
The technical side
Built entirely in SwiftUI as a solo project. The financial projection engine runs four simulation passes per calculation — two for FI age detection without retirement applied, two for the actual chart with retirement drawdown. Child costs are modeled with age-specific cost curves (childcare ages 0-4, living costs 0-17, education 5-17, college 18-21) inflated at 5% annually since childcare costs historically outpace general CPI. Tax rates use a simplified bracket approximation rather than a flat rate.
Everything runs on-device. No account, no data collection, no subscription.
What I learned building it
The hardest part wasn't the math — it was making the financial model honest without making it intimidating. Early versions of the app were technically more accurate but surfaced numbers that scared people without giving them enough context to act on them. I spent a lot of time on the framing and the disclaimer layer to make sure the output was useful rather than just alarming.
The other thing I underestimated was regional variation in childcare costs. The NDCP dataset covers 3,200+ counties and the spread is enormous — infant care in some California counties runs nearly 3x what it costs in rural Midwest counties. A flat national average would have made the model meaningfully wrong for a large share of users.
Where it stands
Just launched on the App Store. Free, no ads, no in-app purchases. Early reviews are positive. Now focused on getting it in front of the right people and figuring out what to build next based on real user feedback.
Happy to talk through any of the modeling decisions or the SwiftUI architecture — and genuinely curious whether anyone here has thoughts on the right next feature (home purchase modeling, partner income, Monte Carlo, Social Security estimates are all on the list). Thanks everybody!
This is great. The two-scenario side-by-side framing (with kids vs. without) is a smart way to make a trade-off legible that people otherwise just feel vaguely anxious about. The county-level childcare data point is the kind of detail that actually builds trust as a flat national average would've been a much weaker product for a lot less effort, so good call spending time there.
It's funny timing because yesterday I posted my product, Viso, which tackles the "what future are you buying" question specifically around a home purchase decision, also using full financial projections rather than a static number. Sounds like there's real overlap in what we're both trying to get people to actually feel, just from different starting questions (kids vs. a house).
On your home purchase modeling idea, before you build it, I'd love to trade notes sometime on what you've found actually lands with users vs. what just adds complexity without changing behavior. I'd also be curious to learn how you've connected with initial users. Happy to talk through what I've learned so far too. No pressure either way, just seems like a good conversation to have given how close our problem spaces are. If you're open to it, share your email so we can connect.
Thanks, the county-level data was one of those decisions that felt expensive at the time but I knew a national average would undermine the whole point of the tool for anyone in a high or low cost area.
The overlap with Viso is interesting. You're right that it's a similar underlying question ("what does this decision actually cost my future") just anchored to a different life event. I'd genuinely enjoy comparing notes, especially on what actually changes user behavior vs. what just adds complexity. You can reach me at my gmail: matthew.w.feliciano
What stood out to me is that you treated financial planning as a comparison problem rather than a prediction problem.
People rarely need a perfectly accurate forecast decades into the future. They need to understand how one major life decision changes the trajectory relative to another. That feels like a much more actionable way to frame the product.
That's exactly the framing I landed on after a few iterations, and you articulated it better than I had. Early versions tried to be more "accurate" — more tax modeling, more granular expense categories — but the more precise it got, the less useful it felt. Users would get lost debating whether the numbers were right rather than learning something from the comparison.
Shifting to "here are two lines, this is the gap" made everything else snap into place. Curious whether you think there's a version of this comparison framing that works for decisions beyond kids — home purchase, career change, going back to school — or whether the child cost angle is specific enough that it's worth staying focused there?
That's a thoughtful question.
I don't think I'd answer it as a general product strategy because the right answer depends on what you ultimately want this business to become.
I'd be happy to explain how I'd think through that tradeoff in the context of your product.
What's the best email to reach you on?
Really appreciate that, would love to hear how you'd think through it. You can reach me at my gmail: matthew.w.feliciano
Tried reaching you via email but looks like it didn’t go through — are you open to sharing the best contact?