Capital budgeting is the process used by businesses to evaluate potential capital expenditures. It involves analyzing projects using techniques like payback period, net present value, internal rate of return, and profitability index to determine which projects to invest in. When starting a new business, entrepreneurs need to estimate capital requirements for initial costs, operational expenses, fixed assets, current assets, and living expenses to determine how much funding is needed. Careful capital budgeting and planning is important for securing necessary financing.