The number itself is not insulting if the offer is presented calmly. Base it on the condition, the limited completed-sales evidence and the certainty you can offer, rather than saying the property is overpriced. Include financing evidence if you have it, offer a useful completion window and set...
A clean structure would be: stated price, brief condition-and-comparables rationale, financing evidence, requested completion flexibility, inspection and finance conditions, deposit terms, and a defined expiry. No commentary about what the seller “should” accept after 79 days. If they counter...