Low income customers have many of the same needs as the rest of the market such as a safe and happy daycare option for their children. The main difference is they do not have as many resources at their disposal, so many have to make tougher choices sometimes with regards to products and services they need. Be respectful of their situation, show that you understand and appreciate their needs and offer them something that speaks directly to them. Most likely they take public transportation, use laundry mats, read the free newspapers available in town, use public health clinics for example. Those are all places you can advertise to reach them with fliers, ads, coupons or brochures. Hope that helps!