Contact the editors of community based publications, for some free space in their paper, announcing your intentions. Enlist the help of printing shops. Some may be willing to contribute their time and supplies, in providing for flyers. These can be posted on public bulletin boards. Post on message boards.
Most major libraries offer Internet access and help.
A bit of foot-work now, can mean the difference between going it alone or forming a solid support system. So far, the focus has been on your ability to physically and emotionally meet this situation. There are other practical, as well as possible legal aspects to consider. Granted, the initial decision to act in this capacity, may have been made under the most amicable environment, it is just good judgment to have this in writing. One never knows what the future will hold and it is for yours, as well as the child s benefit, to cover all the bases.