AmeriTrade requires 40% equity unless ANY becomes 50% of your account. Then the requirement is 50%. If it becomes 70% of the account the requirement becomes 70%.
Their requirements for most small caps is 30% - 40% - 50% so I imagine ANY will be changed to that once it has been trading for a while.
Streaming--Interactive Brokers, which I don't use, has by far the lowest margin rates (2%-3%, I think) and is generally regarded as the cheapest. I think they will margin anything over $2.