Hi, If you can't get into pre-k programs due to financial restrictions, and if your family is not qualified to participate in a local Head Start program ( http://eclkc.ohs.acf.hhs.gov/hslc/HeadStartOffices )...

Some preschools offer scholarships. You can contact potential preschools in your area and ask about their financial assistance offerings, or here's a video about scholarship money for preschool: http://www.ehow.com/video_4790646_free-scholarship-money-preschool.html
 
I'm also including links below to some resources on Education.com you may find helpful.

Have you considered non-profit preschools such as FUMP (First United Methodist Preschools). They are generally affordable and run on a national cirrculum. Yes they are christian based but offer a loving and encouraging environment for children to learn. And most of them even offer scholarships. From experience, they offer 3 day to 5 day half day programs. This generally depends on your location and the need in your community. Good luck in your search.