While not a perfect science, dividing the sale price by the square footage gives you a baseline.
If similar homes in the area sell for $250/sq. ft. and the house you like is 2,000 sq. ft., a fair value starts around $500,000. how to value a house to buy
Asking prices are often just marketing strategy. Only look at what homes actually sold for in the last 3–6 months. While not a perfect science, dividing the sale