Commencing a private investigation enterprise is not merely about acquiring the necessary investigative acumen, but also involves a keen understanding of business mechanics, particularly financial management. Hence, crafting a viable budget is primordial to ensure sustainability and growth. The subsequent paragraphs will provide a comprehensive exposition on the creation of a budget for your private investigation business.

The very genesis of the budgeting process lies in understanding the various expense categories intrinsic to a private investigation business. At its core, this business is a service industry, requiring human capital, equipment, software, and transportation, among others. Let's delve deeper into these categories:

• Human Capital: A sound private investigation business is built on the foundation of skilled investigators. A portion of the budget must be allocated to salaries, training, and benefits. While the actual amount can be influenced by various factors, including the cost of living and competitive salaries in your area, it is pivotal not to underestimate this cost, as the employees are the beating heart of the business.
• Equipment: Private investigators necessitate specialized gear, encompassing covert cameras, surveillance vehicles, specialized software, and more. Although these initial investments might seem steep, they are central to the execution of your tasks.
• Software: In the digital age, investigators need robust software to manage cases, track time, and maintain a digital repository of case files. The budget needs to account for the acquisition and maintenance of such software.
• Transportation: Given the nature of the work, private investigators frequently need to travel. Costs for vehicle maintenance, gas, and potential travel to distant locations should also be factored into the budget.
• Overhead Expenses: These are the running costs of operating your business. It includes rent, utilities, office supplies, insurance, professional fees for services such as accounting or legal counsel, and marketing efforts.

Now that we have established the who and what of the budget, it is crucial to expound on the where, when, and how.

By employing a Zero-Based Budgeting (ZBB) approach, which gained popularity in the late 1970s under then US president Jimmy Carter, every expense must be justified for each new period. It starts from a "zero base" and every function within the organization is analyzed for its needs and costs. This approach allows for a more detailed understanding of where each dollar is being spent, thus lending itself to more informed decision-making.

The application of the ZBB approach involves five essential steps:

1. Identify your goals: Establish what you hope to achieve in the short, medium, and long term with your private investigation business. This will guide your budgeting process and ensure that your financial planning aligns with your objectives.
2. Gather data: Accumulate information about your costs and revenues. It is crucial to be as accurate and comprehensive as possible for a more precise budget.
3. Analyze: Scrutinize all your expenses and evaluate their necessity. Question each cost and consider cheaper alternatives.
4. Create the budget: Based on the analysis, allocate resources to each expense category. Remember, every dollar should contribute towards achieving your goals.
5. Monitor and adjust: Continuously keep an eye on your expenditure and compare it with your budget. If discrepancies arise, investigate the cause and adjust as necessary.

The 'when' of the budgeting is a continuous, cyclical process, starting anew at the beginning of each fiscal year, but incorporating regular reviews and adjustments throughout to ensure the business remains on its planned financial track.

The 'why' of budgeting in the private investigation business, or any business for that matter, is to ensure financial sustainability and profitability. It provides a roadmap for spending and revenue collection, aids in the identification of potential financial issues before they become significant problems, and assists in decision-making related to business expansion and capital investment.

In conclusion, understanding the cost structure of a private investigation business and engaging in diligent budgeting using methodologies like Zero-Based Budgeting can significantly enhance the financial stability and growth potential of your venture. Remember, a successful private investigator is not just a master of investigation but also an accomplished businessperson.