https://innago.com/replacement....-reserve-spreadsheet
Building replacement reserves requires foresight and consistency. Begin setting aside funds as soon as you acquire a property, even before major repairs are necessary. A regular, consistent contribution to your reserve account will ensure that you’re prepared when significant replacements or repairs are required, such as roof replacement, HVAC systems, or plumbing updates. Typically, setting aside 3-5% of your property’s rental income each month is a good starting point, though this can vary depending on the property’s age and conditi