It takes at the very least TEN years for Peyote to start developing mescaline. I think more realistic time estimates would be more like 15-20 years, though.
So even if you could obtain the seeds or a tiny cactus, you're going to need this other tool called "patience". And it has to be a very big patience, if you know what I'm saying.
You should really look into other mescaline-bearing cactii.
If you really were determined to grow a Peyote, however, it's simple if you can avoid the simple mistakes. One of the biggest mistakes people make with cactii is using tiny pots. They only slow the growth. The other mistake people make is assuming that cactii only need to be watered once every few months. They *can* survive that way, but they don't grow. Water your cactus once a week.
So let's go over what you do:
1) buy a pot that looks a bit bigger than you'll need. I'd go with something with a six inch opening at the top.
2) get the best soil you can. The better the soil, the more nutrients. The more nutrients, the faster the growth.
3) get some plant food sticks to put in the soil.
4) plant the cactus.
5) water once a week.
6) rotate the pot 180 degrees every two weeks or your cactus will grow deformed.
7) by the time you've completed 8 years of college, are married and you've had your second kid, your cactus should be ready to eat. of course you probably won't care anymore, but hey, you were so cool for growing this thing! Fuck, wait a few more years and give it to your kids when they get into high school!
These instructions can be applied to any type of cactus, minus #7.
Additionally, you'll have better luck using bottled water. I never water my plants with chlorine-contaminated tap water. Spring water will do. Mineral water is a good treat. And club soda will make any plant grow at an accelerated rate because of the carbonation. But I've never used club soda exclusively, so you may just want to use it as a monthly treat.
In previous threads, other people on this board have claimed that injecting a Peyote cactus with dopamine will increase mescaline production because it's a precursor. However it's only a theory that it would work. Simply giving the cactus dopamine doesn't mean it will neccessarily process it. Also, I think it'd be much more effective to mix dopamine in water then water your plants. It'd be distributed much more efficiently.
And you will also get more growth out of your cactus if you leave it outside during the summer, assuming it's not going to drop below 65 during the day and 50 at night.