Rental yield on a property in Egypt: how to calculate gross and net yield
Gross rental yield is one year of rent divided by the property price, times 100. Net rental yield subtracts the owner's yearly costs (vacant months, maintenance, management, service charges) from the rent first, so it is always lower and closer to what you actually earn.
Comparing payment plans: cash vs installments, short vs long plans
Do not compare the sticker prices alone. Start with the total you pay under each plan, then turn every future payment into its value today at a yearly rate you choose; the plan with the lower present value is cheaper at that rate. The rate that makes the installment plan equal the cash price is its implied yearly cost.
Down payment and installments: how a developer payment plan is calculated
The down payment is a share of the unit price paid at signing; the rest is divided by the number of installments, which equals the plan's years times the payments per year. A discount changes the price the down payment or the rest is worked out on, while the maintenance deposit is a separate amount on top of the unit price.
ROI on a property in Egypt: how to calculate it, and how it differs from return on equity (ROE)
ROI on a property is your net gain (sale proceeds plus net rent, minus everything you paid) divided by everything you paid. Because a property is held for years, convert it to an annual rate before comparing. ROE answers a different question: the yearly net income relative to the equity you actually own in the unit.