Inherited property should be appraised for value as soon as possible after the death of the owner. In the case of financial items - bank accounts, stocks, bonds, bullion - that is easy, and no appraisal is necessary. Physical assets such as real property and collectibles and family heirlooms, those are hard and if they are valuable items, an appraisal is almost a necessity.
The reason is that when you inherit, you inherit at the value of the asset on the date of death, or reasonably close. Your cost basis of that asset is the inherited value, not what the deceased owner paid for it. In most cases, assets you sell immediately after you receive them will not generate any kind of gain to be taxed. Anything you profit on by sale in under a year is taxed as regular income. If you hold it for more than a year, then you receive the more-favorable capital gains tax treatment.
Let's say you inherited ten gold bullion coins worth $1,200 each on the say the owner died - the market price of gold is published daily. Six months later, gold shoots up in value to $1,400 per coin and you don't know if it will go higher or go back down, so you decide to sell them. You have a $2,000 short-term profit that will be taxed as regular income. If you wait until a year has passed and the price you sell at results in a profit, you will pay less tax and maybe no capital gains tax at all, if your regular income is low enough.