We have a 25,000 gallon in ground pool with a gunite liner. We also have no air conditioning, so I love my pool very much.
If you decide to get one, definitely get a Dolphin or similar automatic pool cleaner. It's like a Roomba for the pool, you just turn it on when you're done swimming and let it vacuum the pool overnight. Much MUCH easier than actually vacuuming by hand.
Yes, you'll be fishing mice and frogs and such out all the time. Nothing to be done about it. A solar cover is also helpful for keeping it warm.
Let's see, what else? Oh, make sure that the surrounding patio is slate or brick or something--not poured concrete. Because when one of the pipes that goes underground cracks, a concrete patio around it has to be jackhammered out and re-poured, while flagstones or bricks can just be dug out at the point of the break.
I spend, hmm, maybe $150-200/year on the pool. I leave it to you to decide if that's a lot or reasonable. Insurance wasn't so very bad, maybe a few hundred $$, but you have to have a really good fence.
A pool, like horses, are considered an attractive nuisance: If the neighborhood kids decide they want to go swimming in, say, December, and they fall in and drown, it's your fault for having an accessible pool--even if you've put up two 6' stockade fences with padlocks on the gates and covered the pool with a locking cover, and the kids trespassed onto your property, cut the locks on the gates or broke down the fencing, and smashed the pool cover in with an axe, it's still automatically your fault for letting the pool exist in their general vicinity. It is a great relief to me that my neighbors' swimming pools are much larger and nicer than mine, they can deal with the trespassers.
Agree w/ whomever said that friends and relatives will trash the place. They will also feel free to show up unannounced, expecting to go swimming. I cured this tendency by going skinny dipping at odd hours
so now nobody shows up unannounced unless they want to be permanently blinded/turned to stone.
On the plus side, it is YOUR pool. In public or membership-type pools, people really do pee in the pool. And poop in it, if they've got the runs. And no, the chemicals do NOT "take care of it," the chemicals actually make it even nastier because the chemicals are designed to react with bacteria, not with urea. When it's your pool, your chances of getting the runs yourself, or getting sick from people being nasty, is minimal. You can go skinny-dipping whenever you like, let your dogs swim in it, plus you don't have to shave your legs before going for a swim. No one is going to yell at you for splashing or hogging the diving board. You can eat or drink anything you like in the pool, and let me tell you, a daiquiri in the summer in the swimming pool is a fine, fine thing.