A person with this position of Jupiter has a broad outlook. Many things are of interest to them. The 3rd house is the house of the immediate environment, contacts, concrete thinking, primary and secondary education, and short-distance travels. Such a person loves to learn and discover new things. They are often called the "eternal student." They have a constant intellectual interest and love to read a lot. They are also very well-informed about what is happening in their close environment.
It should be noted that Jupiter in the 3rd house strives to know, read and learn a lot, because in this space, it feels confined. Jupiter is a planet of expansion, while the 3rd house is a limited space. It is a very specific and narrow house (symbolically it is the house of Mercury), so the person here, as if, cannot get enough of knowledge. They study one thing and then another. And, indeed, they know a lot, but often in bits and pieces. And the downside is that they can set small goals, not seeing the big picture. "A bird in the hand is worth two in the bush" - this is about them.
When specific information is needed, the person may start philosophizing. They begin from afar, almost from the very origin of humanity, from the first mention of the topic by prehistoric people. They disperse a lot.
However, this position is very good for advertisers, PR people and real estate agents. Here, they can authoritatively advertise an object, so that there will be no doubt in the choice. It is also a good indication of the profession of a teacher or a travel agent. When telling something, they make an impression of an authority, a knowledgeable person.
Of course, with such a position, the person loves to travel a lot.
They have a fairly wide circle of communication, many friends, acquaintances. And in this society, there may be high-ranking people, people of great authority, or famous people. Famous people or respected professors may live nearby. Or the person themselves may live in a prestigious, expensive area.
This is also the house of our brothers and sisters. Therefore, it may indicate that the person has many brothers and sisters. Relatives often turn to them for advice.