I built a free personal finance toolkit for Spain (FIRE calc, mortgage affordability, historical retirement backtester): feedback welcome

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been building this on and off for a couple months: mirumbofinanciero.com , spanish-language site with a handful of calculators: how much house you can afford, buying costs (property transfer tax varies a LOT by region here, most calculators get it wrong), compound interest, savings rate, and a FIRE calculator that actually accounts for spanish capital gains tax + public pension instead of just doing the generic 25x thing. the one i'm most proud of is a historical backtester, runs your retirement plan against every actual US market sequence since 1928 (like ficalc.app/firecalc) but lets y

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AI 分析

痛点：通用 FIRE/房贷计算器忽略西班牙地区差异（房产转让税按自治区不同、资本利得税、公共养老金），导致结果普遍算错，用户需要本地化且精确的计算工具。

目标用户：西班牙的 FIRE 追求者、首次购房者、正在做退休规划的西语用户，以及为其提供建议的理财顾问。

证据：buying costs (property transfer tax varies a LOT by region here, most calculators get it wrong) ... a FIRE calculator that actually accounts for spanish capital gains tax + public pension instead of just doing the generic 25x thing ... runs your retirement plan against every actual US market sequence since 1928 ... compare different withdrawal strategies (fixed 4%, VPW, guyton-klinger guardrails) side by side ... no signup, no ads yet, calcs run client-side

变现：1) Freemium：基础计算器免费，付费解锁多策略并排对比、方案导出 PDF、自定义假设与本地保存；2) 房贷/保险/券商联盟佣金（购房预算计算器天然贴近成交场景）；3) 把公式引擎作为 API/白标授权给西班牙的理财顾问与 fintech。

MVP：两周内只做「西班牙购房总成本 + FIRE 税务」两个计算器：内置 17 个自治区转让税/印花税规则表 + 资本利得税与养老金抵扣逻辑，结果页可一键生成可分享的 PDF/链接，页尾用邮箱等候名单验证付费意愿，先不碰历史回测这种重功能。

竞品：ficalc.app、firecalc.com、西班牙各银行官网的房贷/储蓄计算器、mirumbofinanciero.com（原帖作者自己的免费站）

摘要：作者用 Next.js 花几个月做了一个面向西班牙的西语个人理财工具站，包含购房负担、购房税费、复利、储蓄率、FIRE 计算和历史回测（1928 年以来所有美股序列，可并排对比 4% 固定、VPW、Guyton-Klinger 等提款策略）。核心差异化是处理了西班牙按自治区差异极大的房产转让税、资本利得税和公共养老金，而这些是大多数计算器算错的点。目前完全免费、无注册、无广告，帖中没有任何付费意愿或收入数据，属于典型的高可行性、待验证付费的垂直细分机会。