Discount brokerages require a minimum age of 18. However, you can create a sub-account under your dads name (as long as he signs some sort of consent form) and these sub-accounts don't have a minimum age requirement.
Vitamin D deficiency rickets can be caused by a lack of vitamin D in the diet, a lack of exposure to the sun, or malabsorption syndromes in which there is an inability of the intestines to adequately absorb nutrients from foods.
Vitamin D deficiency is often a silent disease. By definition, rickets occurs in children whose growth plates have not fused. These children are often found to have started walking late or prefer to sit down for prolonged periods. In adults, vitamin D deficiency results in osteomalacia, which presents as a poorly mineralized skeletal matrix. Adults in these cases can experience chronic muscle aches and pains. Vitamin D deficiency is the most common cause of nutritional rickets. Rare genetic forms of rickets occur because of defects in vitamin D metabolism.