I'm going to emphasize what Streetcar has said. If there are more than 10 breeders in the US breeding true medium variety poodles by using FCI medium poodles imported from Europe, I'll be happily surprised.
As desirable as that perceived size is for many families there are stumbling blocks. Streetcar mentioned confirmation and this is important.
You may not know that there simply aren't a huge number of quality, conscientious breeders to choose from, regardless of what variety, color, and pattern they have in their breeding program. These breeders are not doing this as a for-profit business. They do it for love of the breed.
Next, medium/moyen poodles are perceived by most new to poodles as a 15"-20" size. In the US and Canada that is a standard poodle per the breed standard. That means the breeder won't likely be using the conformation show ring to prove that their dogs meet the breed standard in temperament, structure, and soundness.
This is because, in spite of the fact that the standard variety starts at 15" there is a preferred height in the show ring, generally over 20". A smaller standard is going to have a very hard time being competitive. Keep in mind, the reason for showing is to prove their dog's quality. The ribbons and bragging rights are a bonus.
That said there are very, very few breeders working with the true medium variety, imported from FCI registry countries, and not just breeding intervariety, which would be a miniature to a standard.
There are a very few reasons for a very knowledgeable breeder to do so, but it won't be just to produce the intervariety size. Most of the breeders doing intervariety breeding are doing it as a business with the intention of producing income.
The litter we are looking at is expected to be 25-30 pounds full grown and around 18 inches tall.
The key word here is "expected". Unless this is a breeder with multiple generations of breeding from true medium poodles, there are standard poodle genes in those puppies. That means the potential for full standard size. Are you prepared for that?
Although standards officially start at 15" at the shoulder (where most folk think a medium/moyen poodle would), you'll see very few under 20-21" or under 35lbs.
In the US and Canada the breed standard calls for miniatures to be 10"-15" at the shoulder. Standard poodles start at 15".
The FCI medium poodle starts at just under 14" and goes to just under 18". This means that many US and Canadian miniatures are in the medium size range. Your "expected" 18" is a standard in any breed standard.
Pavie has put in some great work to classify a number of PF poodles. The third and fifth graphs show the range of miniatures and standards.
The suggestion for a miniature ia a good call because if they go oversize, as you'll see several are in the graph, they'll still not exceed your preference,
They're not likely to hit it either. 30lbs, let alone 35lbs is not common, even with oversize minis.
Since standards are typically starting their "small" side at your upper limit, and there's no way to guarantee that a smaller pup from small parents still won't outgrow them noticeably, they're very much a roll the dice choice.
That sweet spot isn't really populated in the poodle world.
All this said, a miniature variety poodle is a great size for apartment, city living, and after they mature are quite capable of taking long walks, go hiking, or just hang out. Temperament is going to be very important for you, as well as poodles from parents properly health tested to the Poodle Club of America recommendations. Knees and hips should be evaluated before breeding.
Picture without some perspective won't be very helpful. I have miniature boys so I'll add a few photos that offer perspective.
It is within the forum rules, so if you care to name the breeder, we can tell you if they're one of the rare, conscientious ones. A search on the Orthopedic Foundation for Animals health testing database will show if there's been any published health testing.
