I agree with Honeysuga about the "rest of my life" kinda thing. All three tattoos I have are related to personal events/people that were in my life and no longer are - the first was a best friend of mine I have lost touch with, and the second two were both in relation to my recently ex fiance. But think of it kind of like a photograph, a moment in time, and THAT's what you are trying to capture. Freezing that moment - no matter what the future holds, what you are feeling AT THAT TIME is what you want to preserve, so even if the things associated with the tattoo are out of your life, you can still remember a happy time.
As far as your questions:
Hurt - it's very dependent on where on your body you get them. Fleshier areas (like your thigh) hurt less. I have one on my left ankle, but higher up near the calf, and it was like, nothing. It's my smallest, and my first tattoo, and I'd put it no worse than an uncomfortable bug bite. My second tattoo is on the back of my neck just under the hairline, and it was a bit more painful, but mainly right in the middle over the vertabrae. The outside edges didn't hurt as much, I'd compare this one to a more painful bee sting. My third tattoo is by far my largest, it covers my entire lower right leg and foot from just in front of my big toe, swirling up over my ankle and ending midway up my calf. It was excruciating. I have a fairly high pain tolerance, and I was close to passing out several times during this tattoo. It took four hours, and I only got one break of about 10 minutes in the middle. The thing is, with tattoos, the longer it takes, the pain builds and kind of overwhelms your system too, so for a first tattoo go with a simple, small design, and don't add a bunch of colors.
As far as cost, again, it's dependent on what you get, and your tattoo artist. I would STRONGLY recommend you find a tattoo artist with a background in artistic studies, rather than a tattooist who was just trained in the shop. My last tattoo is gorgeous, has been featured as a portfolio piece in Body Mod magazine, and the girl who did it was new to the tattooing world but had graduated with a degree in art. She truly IS an artist, I also own two of her paintings. My first tattoo is a simple celtic knot, all black, with two initials (mine and my old best friends - she also has a matching tattoo), and it's about 1/2 inch tall and 2 inches long, and it was only 40 dollars, but that was 12 years ago. My second tattoo is about 4 by 4 inches, a bit more involved (star with ivy growing over it, all black with some green shading around the outside, and a kanji in the middle) and it was 75 dollars. My last tattoo, which is reverse shading of a "breeze" with cherry blossoms floating on it, is all together about 12 inches tall, maybe 5 inches wide at the widest part, 6 different colors used on the blossoms, and I got an AMAZING deal getting it for $450.00 (it should have probably cost me about $650).
In care for it, each tattoo artist will give you different opinions. I've treated all three of mine the same. They come home wrapped in saran wrap, and I leave the saran wrap for the first 12 hours, then I GENTLY RINSE in lukewarm water (not cold, not hot) because the tattoo will leak plasma for a few days. I keep the plasma rinsed off, but be careful not to use a washcloth or anything to wipe it, just rinse with your hands, and careful not to scratch it. I don't keep it covered with the saran wrap after the first 12 hours, but I rinse it a couple times a day, and salve it down heavily with A+D ointment after each rinsing. I don't let it scab and don't let it dry, I know some people do.After the first week with the A+D ointment, I'll switch to a good moisturizer that doesn't contain perfumes/dyes etc. It will itch for a good couple weeks but in my experience using this method makes it heal quickly, and perfectly without losing any color, sharpness, or quality.
As far as touch ups, none of my tattoos have ever needed a touch up, even the one that is 12 years old. It depends again on the colors you go for. I suspect my last tattoo, the one with the cherry blossoms, will need touched up eventually because I have some "light" colors on there (white, yellow, pink, turquoise, red). White or yellow fade VERY quickly on a tattoo, followed next by most pastel shades. Simple black lines last the longest with little to no touch ups needed.
How to choose ~ when you know, you'll know! I have never gotten a tattoo just for wanting a tattoo, each of mine is symbolic and relevant to what was happening in my life at the time, so it was never a question of what tattoo to get, but who to find that can do it for me? I'm a big fan of designing your own tattoo, that makes it particularly meaningful. There are hundreds of thousands of portfolios on the web of tattoo designs, particularly tribals. Spend some time scanning pictures, find something you like as a base, and then work with it to make it your own!
Good luck, and when you decide you are ready, show us what you get!