Some men determine the minimum age of woman they can date by dividing their own age in half and adding 7 years to that. So for you the youngest you could go would be 26.5. To me that rule has always seemed sort of reasonable, but keep in mind that a lot of women aren't comfortable with that big of an age gap. And personally I have to admit that I am more comfortable with someone within 5-10 years of my age. It might well be safest to search within ten years of your own age.
Age difference tolerance for marriage is an individual thing and each person has their own views, so it is best to check out what is written in a profile carefully, and not assume anything. Just as a general observation, successful marriages usually are partnerships where the husband and wife carry their burdens and joys together with an acknowledgement of their respective strengths, weaknesses and roles. That is a lot harder to achieve with a spouse that is young enough to be one's child because age gaps are life experience gaps also.
The biology of fertility and Catholic values are two things that are generally not well understood in society. Making decisions based on pop culture stereotypes may take you down the wrong road in life. Men who are seeking younger (in some cases much younger) women with the goal of fertility in mind should remember that a younger woman or even the man himself may have a medical problem related to infertility. A husband or a wife is not a means to an end - they are a human being. Many women in their forties can conceive. Men who don't look like Brad Pitt or make his kind of money can still be fathers. You marry a human being, and not a thing that can give you offspring or buy you nice jewelry. Marrying is not an acquisition, it is a merger.
And, a lot of Catholics talk a good game about being pro-life and supporting adoption, but few consider the follow-through of taking action to adopt. If a couple marries, and whether by age or by medical condition they cannot bear their own children, there are children who need a loving and stable home. If the desire for parenthood is there, you can still make your own family.