Read this article to discover the answer. Oyster mushrooms can be grown as fast as 20 days while truffles will take over 10 years before you even know if the mushrooms will fruit! Of course this is from inoculation to fruiting. If you are buying a grow kit and just fruiting it takes about 10 days for mushrooms to form.
Mehta (1982) highlighted the problems being faced by mushroom growers. He pointed out that compost and spawn availability, transportation of raw materials, high cost and non-availability of compost and spawn were the main problems.
Compost provides nutrients needed for mushrooms to grow. Two types of material are generally used for mushroom compost, the most used and least expensive being wheat straw-bedded horse manure