The kallah's parents can't help financially, or the family is simply poor — is that a reason to decline?
A family's poverty is not a reason to decline: what matters is the person's character, and providing for the couple is in Hashem's hands — a shidduch should not be held up over money. Some even see an advantage in a kallah from a home without means, while allowing that a home full of Torah is also a virtue — the point is not to let outward circumstances blind you.
Since you write yourself that the young woman suits your son in character, that is the most important thing in a shidduch and in building a family. The material side is Hashem's concern: He will help, and in the early years of married life the young couple will most likely be supported by parents on both sides. From this comes the general rule the Rebbe states outright: a shidduch must not be held up over money. In another response he adds that, by plain and simple reasoning, there is no room for a few thousand to hold up something called a 'binyan adei ad' — an everlasting structure; and when only the other side is holding things up, the right path is to find friends who can influence them. He does not forbid negotiating over money as far as possible — but the shidduch should be brought to completion at a good hour.
The main thing in a shidduch is that 'he who finds a wife has found good.' Financial support is in Hashem's hands: a person's livelihood is decreed on Rosh Hashanah, and no one can guarantee it, so this is no reason to turn away a good find. A young woman with good middos is not rejected over money — good middos are the most important quality, and that is what a person should seek, to the extent they are able to recognize it.
To a student who returned from a first meeting saying, 'such poverty… terrible poverty,' he answered with a question: 'and what other good qualities did you see in them?' That was always his answer whenever the subject of a kallah from a poor home came up, and he genuinely considered a girl's poverty an advantage — the opposite of today's common view.
“And what other merits did you see in them?”
It is not for nothing that Chazal taught to cherish the children of the poor, since it is through them that Torah goes forth: if a person wants to be someone who spreads Torah, there is good reason to look for a wife from a family without means. He immediately qualifies this, saying he is not claiming there is no advantage in marrying a girl from a home full of Torah and fear of Heaven, if she is otherwise suitable. The point of his advice lies elsewhere: look in a girl for what matters most, and don't let impressive outward circumstances blind you.
“let us not allow ourselves to be blinded by impressive outward factors.”
