For solo founders dreaming of financial independence through a Micro-SaaS, the ultimate question is often personal: can this business actually pay my bills? We’re moving beyond vanity metrics to a concrete 2026 reality: your mortgage. Let’s break down exactly what it takes for a 100-user product to become your primary income source.
The Core Financial Equation: MRR vs. Mortgage + Overhead
A 100-user Micro-SaaS can cover a $2,000 monthly mortgage and basic business costs in 2026, but only under specific conditions: an average revenue per user (ARPU) of at least $45, a monthly churn rate below 3%, and operating as an S-Corp with disciplined expense tracking. After estimated 25% effective tax, the required gross MRR is approximately $3,650.
Most analyses treat your housing cost as a personal expense, but for a founder relying on the business, it’s a fixed liability—just like a server bill. It gets paid first. Let’s say your mortgage is $2,000 and you need a $500 monthly buffer for unexpected business costs (a software license, a quick freelance design fix). That’s $2,500 you need to take home after taxes.
Here’s the critical pivot most miss: you don’t just need $2,500 in MRR. You need enough MRR to cover taxes and then net $2,500. A realistic effective tax rate (combining self-employment and income tax) for a solo founder is around 25%. So, your target Gross MRR is: ($2,000 + $500) / (1 – 0.25) = $3,333. We’ll round to a cleaner $3,650 target to account for minor fluctuations.
- Action: Calculate your non-negotiable monthly nut: Mortgage + Insurance + Property Tax + $500 business buffer.
- Action: Use the formula: Gross MRR Target = (Your Monthly Nut) / 0.75.
- Action: Open a separate business savings account and transfer 25% of every payment received to it, for taxes.
The 100-User Constraint: Pricing, Churn, and Realistic ARPU
With a hard cap of 100 users, your pricing and churn aren’t just metrics—they’re survival levers. To hit $3,650 MRR with 100 users, your Average Revenue Per User (ARPU) must be $36.50. But churn changes everything. If you lose 3 customers a month (3% churn), you need to replace them just to stand still, which costs money and time. This forces your effective ARPU higher.
Consider this trade-off: A niche B2B tool for architects might command $80/month, but attracting those 100 users is slow. A consumer Chrome extension could get to 100 users quickly at $15/month, but the math implodes—you’d need over 240 users at that price, blowing past your constraint.
Here’s a simple matrix for the $3,650 target:
- At 2% monthly churn, you need ~$38 ARPU.
- At 3% churn, you need ~$45 ARPU.
- At 5% churn, you need ~$58 ARPU.
Hypothetical: “Founder Alex” has a $40 ARPU and 5% churn. They’re losing 5 users ($200) monthly. To net out, they must spend time and money acquiring 5 new users just to stay at 100, burning cash that should go toward the mortgage. The high churn makes the target unreachable.
- Action: Model your required ARPU using: ARPU = Target MRR / (100 * (1 – [Your Churn Rate])).
- Action: If your planned price is under $40, validate if your target market has ever paid that much for a solution.
- Action: Build a simple cohort retention chart from day one to measure true churn, not just net user growth.
Post-Launch Realities: The Hidden Costs After $3,650 MRR
You hit $3,650 MRR. Congratulations! But your mortgage-paying cash isn’t $2,500. A new layer of operational costs emerges that scales with your success. These aren’t startup costs; they’re costs of doing business at this level.
First, payment processing. At $3,650 in charges, Stripe/Braintree fees (2.9% + $0.30 per transaction) could easily be $130-$150/month. You’ll likely need a dedicated customer support tool (like Crisp or Help Scout) for $50/month. If you wisely formed an S-Corp for tax savings, you now have payroll service fees (Gusto: ~$40/month) and must pay yourself a “reasonable salary” through payroll, which involves its own withholding, further complicating cash flow.
The profit margin you modeled is often consumed by the tools you need to manage the success you’ve created.
Mini Case: Your SaaS uses an external API that costs $0.10 per user action. At 100 users, activity grows, and that API bill jumps from $50 to $200/month. This wasn’t in your initial “business buffer.”
- Action: Audit your recurring costs at $0 MRR, $2k MRR, and $4k MRR. Include payment fees, support, and infrastructure.
- Action: Factor in a 3-5% “transaction cost” on your MRR for payment fees before calculating profit.
- Action: Talk to an accountant about S-Corp salary requirements before you hit your target MRR.
Scenario Analysis: Mid-City Mortgage vs. Business Model Fit
Your mortgage amount isn’t just a number; it pre-selects your viable business model. A $1,800 mortgage in Columbus, OH, requires ~$3,100 Gross MRR. A $2,300 mortgage in Denver, CO, requires ~$3,730. That $600 difference in required MRR might mean you need a $50 ARPU instead of a $40 ARPU, which is a fundamentally different, more niche product.
Let’s map models to mortgages:
- High Mortgage ($2,200+): You’re forced into B2B or niche professional tools. Think a $79/month project management add-on for legal firms. Long sales cycles, but high ARPU and lower churn.
- Moderate Mortgage ($1,600-$2,000): You have more flexibility. A $49/month productivity SaaS for freelance developers could work. Balance of attainable audience and sustainable price.
- Lower Mortgage (<$1,500): Wider options, including premium B2C. A $29/month health and wellness tracking app might suffice, though B2C churn remains a major challenge.
The key takeaway? Don’t fall in love with a B2C idea if you have a Denver mortgage. The numbers will betray you.
- Action: Research the median home price/property tax in your city to gauge a realistic “founder mortgage” for 2026.
- Action: Cross-reference your required ARPU with real products serving that price point. Are they B2B or B2C?
- Action: If your heart is set on a low-ARPU model, calculate the user count needed (e.g., 300 users at $20) and be honest about the acquisition feasibility.
Decision Framework: When to Bet on 100 Users, When to Pivot
How do you know if you’re on the viable path or a slow burn to zero? The signals appear in your first 6-8 months. The constraint isn’t the 100 users—it’s the time and cash it takes to get there while covering your mortgage.
You should seriously consider a pivot if:
- Your Month 4-6 gross revenue churn exceeds 4%. At this rate, the 100-user model is mathematically unstable for your mortgage goal.
- Your Customer Acquisition Cost (CAC) is more than 1.5x your ARPU. You’re spending too much to refill the leaky bucket.
- You cannot reach 40 paying users within 6 months of serious effort. The path to 100 is too long for your runway.
Double down if: Churn is under 2%, you’re seeing organic sign-up growth, and you have a clear path to increase ARPU through a premium tier.
Run a simple runway check every month: Months of Coverage = (Your Savings) / (Mortgage + Business Costs – Current MRR After Tax). If this number is shrinking faster than your user count is growing, you have a problem.
- Action: At month 4, calculate your gross revenue churn. If >4%, initiate a deep retention interview campaign immediately.
- Action: Track your “Months of Coverage” on a simple spreadsheet. If it dips below 6 months, you need a drastic change (e.g., consulting work, cutting costs).
- Action: Pre-define your pivot trigger (e.g., “If not at 40 users by Month 6, I’ll shift to a service model”). Write it down now.