I got my ACE certification last fall, studied for about two months, spent a day getting my CPR/AED cert, then spent 2 hours taking the exam for the ACE cert. Bang, boom, done. Any certification is going to cost you some money to earn but that's very easily recovered within your first few clients.
The guys here have already given you good advice, make sure you are open to and knowledgeable about other training methods than just strength training because that's definitely not what everyone wants.
MARKET YOURSELF.