If you own a shop, you can register your business as one DTP centre, further, you can make arrangements for attending the customers, placing your computer and accessories.
Try to build up a good network of local printers and publishers, to give your business a complete roundup.
Try both online and offline customers. Once you start getting orders, depending on the demand, you can go ahead with employing a couple of helping hands, later on. But I would suggest, to start off as a freelancer, without going in for much investment right at the moment. Once you are capable of creating a stable clientele, you can slowly build up your business with proper investment.
Have you joined any Facebook Group? In Facebook, you would find groups for almost every kind of profession you can imagine. Search for DTP. You would definitely find a number of groups there. Join as many as possible. Reply to the posts where people are looking for work to be done. You can post your own business in a short detail. First, keep your rates low. Once you start getting assignments, you can increase it further.
Same on Linked In.
The other good option is creating a website for your enterprise. Build it up with payment gateways. Make a place to show up your skills, products, packages and services. Add buttons for clients to place an order. Then share your website with as many places as you can. You can even choose to advertise on Google AdWords and other places at some fee. At the same time, you can even earn a small amount through Google AdSense.
You can even contact the publishing houses and ask if there is any chance for you to deliver. Try to add a few more related services, so that people get to see some more benefits from your enterprise.
Hope this would work. Wish you all the good luck. Feel free to ask questions whatever crosses your mind. You can post your queries in the Ask Expert section too. That way, you would get a small token of cash credit as well.