If you're buying a house, it's worth having a good home inspector (Get references!) check the basement and give you an educated estimate of how well the drainage and sump system, if any, is working, as well as any risk factors based on how the basement is built. And know that even the very best home inspector can only give you an educated opinion. Unexpected things can and will happen.
Here's my experience with basements and houses over the years, and what I've learned:
The house I grew up in was a ranch, built new, with poured concrete walls in 1970. It was built on fairly high ground, on sandy southern Michigan soil. It never leaked, and stayed at a comfortable temperature all year; just needed a dehumidifier in summer and a few vents in the overhead ducts opened in winter to add a little heat. There was a sump, but its only purpose was to pump the drain water from the washing machine and the dehumidifier up to the sewer line that ran to the septic system. When the house was about 10 years old, a small bit of seepage developed in one corner because the soil between the house, the detached garage, and the walkway between had settled and wasn't draining as well as it had before. Extending the downspout from the gutters on that corner by a couple of feet fixed it forever.
In the 90's I moved to a house that had been in the family for years, down in Indianapolis. It was in a subdivision built in the 1940's, with a concrete block basement. That basement was dry as can be until I-465 was built around the city. Then, gradually, it became more damp as the highway system changed the city's drainage characteristics in a way that the ancient storm sewer system was never designed to cope with. Once I-465 was complete, the "ring" of concrete and berms around the city trapped a lot more ground water than before. That combined with the clay soil that drains poorly once it's saturated made for a frustrating increase of seepage and runs in the basement. I spent a lot of time scraping the painted block walls, applying sealant and DryLok paint, plus filling and smoothing the joint between the floor slab and the wall with hydraulic cement (It swells and forces its way into voids when it's wet). A lot of work, but the basement was dry again, although the dehumidifier was essential almost year-round. In most cities, any house inside of a large perimeter highway system risks at least dampness in the basement unless the basement and lot is either designed or re-worked to handle the increased water table that results. Few cities have the means to mitigate with improved storm drainage.
In the early 2000's my new family moved into a bigger ranch house on a crawl space, still in Indianapolis. No basement to flood, but the crawl space could be damp, even after putting a vapor barrier down, which tended to increase humidity in the house and overwork the air conditioning. I came to dislike the house over time; the garage was mostly filled with storage that should have been in a basement, and the house was big and spread-out enough that a full basement would have been a huge benefit... but no such luck.
My work took us to New Hampshire in the mid-2000's. We first rented an old "New Englander" style house in a town near the seacoast while I worked down in the Boston area. Everything with a basement in the area tended to flood; the water table was high since this was the coast, and most of these old houses had stone foundations. This one had been raised some time ago and had a poured concrete basement put in. It was a shallow basement, too. It stayed dry, but being only halfway below grade, it tended to be hot in the summer and cold in the winter. It was also my first experience with typical New England home designs -- they have a small footprint, and just build up into one-and-a-half and two-story designs. It saves money digging and blasting in rocky soil, but it really limits basement size. We had to use the loft in the accompanying barn for additional storage. Actually, I think the barn roof never leaked, but the house roof did...
With a change to a better job, we moved inland to a house built in the 1920's. The basement was a little bigger, though this time we still needed to store a lot in the attic of the house. (A walk-up attic, which is a nice concession when basements are still small by my reckoning.) This basement was all mortared stone and the house had a stone retaining wall built out from the basement walls, too. That's a lot of stone for water to get past! The home inspector looked it over, and to him it appeared bone dry and likely to stay that way. And it did. Until the huge retirement home community in the neighborhood decided to expand, and messed up the drainage so that their runoff started flooding the homes in the neighborhood. Most got feet of standing water in their basements. I got an inch running across the floor into the floor drain, enough that I could get everything that wasn't already off the floor up on blocks and out of harm's way. After the water receded, I built channels around the perimeter to direct any seepage into the floor drain. It worked well, but we could never stay ahead of the dampness, which caused mold issues upstairs and affected my wife's health. We had to sell it and go back to renting...
We rented a couple of houses over the next years. Both were newer, with the all-too-common garage under the house, taking up most of the basement. Garage doors never insulate all that well in New England, so they're hot or cold depending on the season, and mice and creepy-crawlies love to get past them. (Kept the cats entertained, though...) Once house had a big walk-up attic that could have been converted to a nice train room, the other had a detached garage with a walk-up attic that could have been converted, but we weren't staying long enough to do that.
Last year, we finally found a decent-size ranch house with a full basement -- nearly 1800 square feet of it. No garage impinging on it; that's upstairs on a slab, attached to the house. A basement that size in any house that's remotely affordable in New Hampshire seems to be scarcer than hen's teeth! It turns out that it was an unusual case -- the lot is all sandy soil, and when the house was built ten years ago, it was on the site of a fuel company's storage depot. So it had to be all dug out and back-filled with clean sandy soil anyway to meet some very strict state environmental regulations. Digging the basement was cheap, since they saved on fill. Saying it drains well is an understatement! The lot drains well; runoff visibly goes away into the neighbors' yards. (They're all on crawl spaces, so they don't get flooded by my lot. If they had basements, my lot would have needed a perimeter drain to direct it to the storm drains!) The basement doesn't even need a dehumidifier running; in fact the air conditioning in the house tends to dry things out too much upstairs; I have to run the system fan on a periodic circulation cycle to pull some of the moister air out of the basement and up into the main floor in the summer, so the whole house tends to balance itself for humidity. We plan to finish this basement for a train room and rec room, with an unfinished section for storage.
I've found there's no substitute for good poured foundation walls. Concrete blocks can fill as the water table rises, and the water pressure will find the tiniest gaps to seep through. Clay soil saturates quickly and drains poorly compared to sandy or rocky soil. So in areas with clay soil, French drains and sump pumps may be unavoidable. Stone walls are known for leaks, but they don't have to be. If they're built well to begin with (Thick!) and are kept in good order with mortared seams and a good coating of DryLok sealant, they can be surprisingly dry if the drainage around the building is maintained well. The same goes for old brick basements, too. They can be dry if the mortar is kept in good condition and given a proper coat of sealant paint. The joint between the slab and the wall is usually the first place that lets water in. If you attack it with hydraulic cement while it's leaking, or after, by actively flowing water over it as you apply the cement, you can seal it up. It's nasty, messy work, but it gets good results if you do it right.
When we were house-hunting, it was amazing how many damp basements we encountered -- even ones with poured walls, built in the 70's, 80's and 90's. Drainage and proper sealing get neglected so often during construction. Good gutters and drainage away from the house also can be a huge help. New England builders hate gutters -- they fear ice dams forming that back up under the roof shingles. Good roof designs and ice shielding under the shingles will prevent it, and building codes and insurers even require the ice shielding whether there are gutters or not, but they just don't want to spend money on gutters. So the roof runoff goes right down to the foundation line, which can eventually work its way into the basement. If there are no gutters on a house, it's often worth having them installed so that the runoff can be directed way from the basement.
Don't overlook those little basement windows, either. Make sure the frames are sealed up well against moisture (and drafts, too, for energy savings!) If they're set down in "window wells" because they're partially below grade, keep the well clear if debris and leaves; the bottom should be filled with sand and/or gravel for drainage. Home and hardware stores sell plastic domes that keep water and leaves out of them.
Particularly on houses without gutters, rainwater running off the roof can splash back and hit the sill where the basement wall and the base of the house wall meet. A home inspector should always check the sill carefully, and you should, too, periodically. Water can work its way in at the sill, getting into the basement and rotting the sill away at the same time, causing endless homeowner misery and expensive repairs if it goes on too long. Did I mention that good gutters are important? They aren't cheap, especially if you have to pull roofing back to add ice shielding as part of the project, but they can head off a lot of expensive water problems down below.
