What the rule of thumb is
A common guide is to budget around one per cent of a property value each year for maintenance.
It is not based on anything precise. It is a rough observation that bigger and more valuable properties have more in them to look after, and it holds up reasonably well across a lot of properties.
What it is genuinely useful for is a sanity check. If you are spending a tenth of what the rule suggests, either you have a new property under warranty or you are deferring things that will arrive later.
If you are spending several times it, either something is wrong with the property or somebody is charging you badly.
It is not useful as a budget on its own, because a rule cannot see your actual air conditioning units. For that, use the itemised tool.
