If your most likely source of income is going to be people you know (and, believe me, it usually is) then go out and talk to them. Do not be afraid to mention, brazenly, to anyone you know who might be interested, that you will be happy to take care of their copywriting needs. Some of them might even take up your offer.
And if not, at least they will be more likely to recommend you if they hear of a copywriting job elsewhere. Running a copywriting business means you need to become an expert in networking, the art of making and keeping contacts.
There is a general, although not universal, rule that the longer you work the easier it is to get new work. This is because, over time, and assuming your work is of decent enough quality, more and more people will come to know about you, either directly or through referrals, and call upon you for help.
In order to get the ball rolling, you have to work hard at building up a network of contacts. This is why it is often easier to start up in business after working in a company within the creative or media industries, where you are likely to come across a number of individuals or organisations that could use your services.