Demand: There is supply and buyers willing and able to purchase the inventory. Opportunity.
Rarity: When there is a limited supply property in particular locations and more buyers want this type, there may still be more demand. Missed sales if the inventory is sold out.
Condition: Affects the demand. If there is a lot of work needed for the property to be in demand, the price needs to be low enough to enable the buyer to pay for repairs and not be paying over the market price. No sale if price is not right.