Ventura Beginner Needs Cheap Surfboard

Hey Everyone... I am just starting out as a surfer! I am a little old (18 years this past July) but I am loving the ocean and surfing. My friends have been teaching me and letting me borrow theirs but I don't want to be a moocher anymore. If anyway has an inexpensive surfboard I might be willing to take it off their hands. I was hoping for something around $100? If that's possible, Thanks! 
