If a man never yet had children, he must seek a "bas bonim" (wife, who in the natural order of the world, would be expected to be capable of having a family) with whom he can fulfill the mitzva to have children, which is a man's first obligation in getting married. A woman who is at or near the end of child bearing years, or who for any reason cannot or would refuse to have children, may only marry a man who has already fulfilled his mitzva-obligation to have children or who cannot have children.

The Torah prohibits, and requires distance from, sheker (falsity, lying). This applies, of course, in all aspects of shiduchim. Therefore, you SHOULD NEVER LIE ABOUT AGE. Rabbi Shlomo Zalman Auerbach says that you cannot lie even the slightest bit. You should certainly never lie or exaggerate about ANY FACTOR that the person would be makpid (strict, particular, angered) about, would hate or resent you over, might break an engagement or marriage over. Without trust, there is no communication or lasting marriage. If you ever catch a shadchan in a lie, you may be allowed to warn others not to deal with that shadchan (check with a rov or the Chafetz Chayim's sefer on lashon hora for guidelines on when and how to tell, for the sake of protecting others). However, lying for peace in an already existing relationship might be allowed.

If a person has done tshuva, the past should not be held against the person. The Torah's story of Rivka shows how we do not hold a bad family against someone who abandons the past and embraces Torah faithfully. If a woman is not a virgin but did tshuva, she does not have to tell this on a first date but she must tell before the man becomes emotionally involved. If he accepts her, her kesuba will be that of a virgin. If a baal tshuva's unreligious mother was previously married and divorced before a second marriage from which this boy or girl was born, you must investigate whether there was (in the mother's first marriage) a kidushin (Torah marriage) and/or get (Torah divorce). A momzer (child of a prohibited relationship) and his/her descendants, till the end of time, can not marry a kosher Jew. A kosher Jew marries a kosher Jew, a momzer marries a momzer. A suffek momzer (a questionable or unverified momzer) is a more stringent case than a confirmed momzer. The Shulchan Aruch poskins that a suffek momzer cannot marry anybody - neither a kosher Jew nor a momzer (perhaps the suffek momzer is the opposite). When any boy or girl in a shidduch comes from a previously married or divorced mother, when there is any question of validity or acceptability of the get or bais din which produced it, a thorough investigation under the direction of a qualified and G-d fearing rov, is mandatory. When there is any reason to fear even a possibility of momzeruss, we must investigate. When there is no reason to fear momzeruss, a Jew has a "Chezkas Kashrus (presumption of being fine)." When a previously married woman is herself a shidduch, I tell men who are seriously interested, to require her permission to take her get to their rov so he can poskin that the get is blemishless and that she is truly available, before they can become involved.

There are various opinions about age difference. The Shulchan Aruch (Evven HaEzzer) itself only prohibits an early teenage girl from marrying an elderly man because the very young person may not remain faithful. The Steipler said that a teenage girl should stay within ten years. We can infer that once she leaves teenage, we can stretch the age difference so that she can marry a man considerably older, judging the coupling by how well the two would get along and suit each other. A woman can be a bit older than the man if they are suitable and she still can supply him with needed child-bearing years.