Passive Income for Python Developers: The Technical Ebook Model That Pays for Itself

Monthly fixed costs:
  Gumroad Creator plan     $20/month
  Claude API (ongoing)     ~$0 (only needed during generation)
  Domain / landing page    $0 (optional)
  ─────────────────────────────────────
  Total                    $20/month

Per-book costs:
  Claude API (generation)  ~$1.50/book
  Cover (automated)        $0
  KDP enrollment           $0
  ─────────────────────────────────────
  Total per book           ~$1.50

Net per Gumroad sale = $12.99 × (1 - 0.10 - 0.03) = $11.21
Break-even sales     = ceil($20 / $11.21) = 2 sales/month

#!/usr/bin/env python3
"""
revenue_model.py — 12-month catalog revenue projection
"""
from dataclasses import dataclass

@dataclass
class BookParams:
    price: float = 12.99
    platform_fee_rate: float = 0.13  # Gumroad 10% + ~3% payment
    launch_sales_per_month: int = 4  # month 1
    steady_state_sales: int = 2      # after month 2
    decay_start_month: int = 2       # when to drop to steady state

@dataclass
class CatalogParams:
    books_per_quarter: int = 1       # publishing cadence
    fixed_monthly_cost: float = 20.0 # Gumroad subscription
    per_book_cost: float = 1.50      # Claude API per book

def model_catalog(
    months: int = 12,
    book_params: BookParams = None,
    catalog_params: CatalogParams = None,
    verbose: bool = True
) -> list[dict]:
    bp = book_params or BookParams()
    cp = catalog_params or CatalogParams()

    net_per_sale = bp.price * (1 - bp.platform_fee_rate)
    books_published: list[int] = []  # list of months when each book published
    results = []

    for month in range(1, months + 1):
        # Publish a new book each quarter (months 1, 4, 7, 10)
        if (month - 1) % 3 == 0:
            books_published.append(month)

        # Calculate revenue from all published books
        monthly_revenue = 0.0
        for pub_month in books_published:
            age = month - pub_month  # months since publication
            if age == 0:
                sales = bp.launch_sales_per_month
            elif age < bp.decay_start_month:
                # Linear decay from launch to steady state
                t = age / bp.decay_start_month
                sales = bp.launch_sales_per_month * (1 - t) + bp.steady_state_sales * t
            else:
                sales = bp.steady_state_sales
            monthly_revenue += sales * net_per_sale

        # Monthly costs
        new_books_this_month = 1 if (month - 1) % 3 == 0 else 0
        monthly_costs = cp.fixed_monthly_cost + new_books_this_month * cp.per_book_cost
        net = monthly_revenue - monthly_costs

        result = {
            "month": month,
            "books_live": len(books_published),
            "revenue": round(monthly_revenue, 2),
            "costs": round(monthly_costs, 2),
            "net": round(net, 2),
        }
        results.append(result)

        if verbose:
            status = "+" if net >= 0 else "-"
            print(
                f"Month {month:2d} | "
                f"Books: {len(books_published)} | "
                f"Revenue: ${monthly_revenue:6.2f} | "
                f"Net: {status}${abs(net):.2f}"
            )

    return results

def summarize(results: list[dict]) -> None:
    total_revenue = sum(r["revenue"] for r in results)
    total_costs = sum(r["costs"] for r in results)
    total_net = sum(r["net"] for r in results)
    profitable_months = sum(1 for r in results if r["net"] > 0)
    first_profit = next(
        (r["month"] for r in results if r["net"] > 0), None
    )

    print(f"\n{'='*50}")
    print(f"12-Month Summary")
    print(f"  Total revenue:       ${total_revenue:.2f}")
    print(f"  Total costs:         ${total_costs:.2f}")
    print(f"  Total net:           ${total_net:.2f}")
    print(f"  Profitable months:   {profitable_months}/12")
    print(f"  First profit month:  {first_profit}")

if __name__ == "__main__":
    print("=== Conservative (1 book/quarter, 2 steady-state sales) ===\n")
    results = model_catalog(months=12, verbose=True)
    summarize(results)

    print("\n=== Optimistic (1 book/quarter, 4 steady-state sales) ===\n")
    optimistic_bp = BookParams(steady_state_sales=4, launch_sales_per_month=8)
    results_opt = model_catalog(months=12, book_params=optimistic_bp, verbose=True)
    summarize(results_opt)

Month  1 | Books: 1 | Revenue: $45.00 | Net: +$23.50
Month  2 | Books: 1 | Revenue: $22.50 | Net: +$2.50
Month  3 | Books: 1 | Revenue: $22.50 | Net: +$2.50
Month  4 | Books: 2 | Revenue: $45.00 | Net: +$23.50
...
Month 12 | Books: 4 | Revenue: $90.00 | Net: +$70.00