There are a lots of highly ranked brokers which doesn’t have a account minimum.
And as you can probably expect here there are some brokers which require a minimum initial investment. And that minimum can be anywhere from $100 to $500 or even more.
There are many mutual funds which also require similar minimum investments. Which in the end means that if you are able to open a brokerage account with a small amount of money, it could be a struggle to actually invest it.