Your gross income is the amount of money you earn before anything is taken out for taxes or other deductions. The overall gross income is calculated as the sum of all transaction lines that have a transaction type in the Income category. The gross income for a property is calculated the same way, but the transaction lines are filtered by that property. Deposits are not calculated as gross income, as a deposit is a liability.
An operating cost is an expense a business incurs through its normal business operations. The overall operating costs are calculated as the sum of all transaction lines that have a transaction type that is in the Expenses category and doesn't have "Exclude transactions with this type from Operating Costs?" set to Yes. The operating costs for a property are calculated the same way, but the transaction lines are filtered by that property. Mortgage principal payments are not calculated as operating costs, as mortgage principal is a liability. However, mortgage interest, PMI, escrow taxes, and escrow insurance are calculated as operating costs.
Net Operating Income
Net operating income (NOI) is simply the annual income generated by an income-producing property or properties after taking into account all income collected from operations, and deducting all expenses incurred from operations. The net operating income is calculated as the gross income minus the operating costs.
Mortgage Principal Paid
Your mortgage principal paid is the amount of money you paid on your mortgage payments that went directly towards paying down the principal balance on your mortgage. The overall mortgage principal paid is calculated as the sum of all transaction lines that have a transaction type that is in the Liabilities category and has "Is for Mortgage Principal Payments?" set to Yes. The mortgage principal paid for a property is calculated the same way, but the transaction lines are filtered by that property.
Net cash flow refers to the gain or loss of funds over a period of time after all debts are paid. The cash gain is calculated as the net operating income minus the mortgage principal paid.
Cash on Cash Invested
Cash-on-cash invested is a rate of return often used in real estate transactions that calculates the cash income earned on the cash invested in a property or properties. The cash on cash invested is calculated as a percentage, by dividing the cash gain by the down payments on all properties.