This document outlines the key steps and considerations for writing a business plan for an ISP, including: 1) Identifying the target market segment and estimating size, uptake, and competitive landscape. 2) Modeling costs such as capital expenditures, recurring costs, marketing costs, and staffing costs. 3) Developing a pricing model based on marginal costs and determining retail pricing for access lines and additional services. 4) Estimating demand, revenue, scaling network capacity, and costs to calculate the bottom line profitability.