Flea Proctetion for Dogs and Cats?

I have a cat and dog in the house and an outside cat. I have heard that Frontline Plus is the best flea and tick drops. But it's so expensive, and I don't have much money to begin with and I was wondering is there anything else that is not as expensive that works just as well? If there is none other, I will buy it, but if there is something cheaper, so any suggestions or comments would be helpful! Thanks a bunch!