To open a brokerage account, it usually costs around $1,000. However, some brokerages will offer programs where you can open a brokerage account with only $100, but you have to set up montly deposits of $100 until the account reaches $1000.
"Most people get interested in stocks when everyone else is. The time to get interested is when no one else is. You can’t buy what is popular and do well." Warren Buffett