Some stocks are required to be bought at at least twelve shares. Are most stocks like that? Is it possible to buy one share (of YAHOO!)?
It's the broker's choice.
Some will buy a single share for you of a stock that sells for $0.07 cents per share, and charge you $75 broker fee.
Others are going to insist that you open an account and put $500 or more in the account, and then you can buy whatever you want without a broker.
There are some who consider to be any stock that trades for pennies or those that trade for under $5, whereas others regard it as any stock trading off of the major market exchanges. Nevertheless, puzzlement can occur as there are some very large companies, based on market capitalization, that trade below $5 per share, whereas there are many very small companies that trade for $5 or more.
I have a Sharebuilder account. You can buy a percentage of a share on there. I recently invested $5 dollars in a stock and purchased .02 of a share.
You can buy one stock of ANYTHING that's over a dollar. The ones that sell for fractions of a cent I really don't know tbh.