I have been certified since July. I have 6 clients that come to my home gym right now. I really prefer to work this way as opposed to working in a gym. I have had a couple of referrals through word of mouth and the others I knew at least as acquaintences when we began. Actually, two of them came to me privately because they take my cardio/sculpt class that I teach ( I do that in a studio). So far, it is going well. Once I finish the gym area ( it is still only half finished) and make a private entrance from the outside of the house, I wll be able to advertise more and take a few more clients. I will also eventually offer my services in a client's home, but not just yet. Right now I feel that those steps need to be taken before I am comfortable having clients that are complete strangers.
Anyway, I think that you will have to figure out where you want to train, and then if you do go with a gym you should be visible and you may have to approach people directly. If not and you plan to work privately, then word of mouth would be your best betas well as putting flyers out and internet advertising. I do think people will pay alot of money to have you come to their home as well, food for thought.
Anyway, good luck. I am absolutely loving this career change and I wish you all the success in the world!