Maybe exempt if the purchase price was a certain amount below the average for the market.
Like if the price per sq. ft / acre of the house was 75% of market average when purchased it’s exempt, that way the houses that really need to be repaired and fixed with get the attention they need to keep them in the market.
Then people can’t just buy a house, slap a coat of paint on it and some new counters then sell for $100k over the purchased price 6 months later.