I have rarely found Cattleyas in flower stores, the best source are orchid growers or the internet. The price range, mostly depending on size, is between $8 and $50.

Light
Cattleya orchids like bright light and some sun. A west or east facing window with direct sun for several hours should work great. A south facing window with a little shade is a good place, too.
I use a light meter to measure the light intensity. For most Cattleyas a light level between 20,000 and 30,000 Lux or 2,000 and 3,000 Footcandle is recommended.

Temperature
Most Cattleyas do well in normal indoor temperatures. They like 70 to 85 F during the day and 55 to 60 F during the night.

Water
For all Cattleyas, let the potting medium completely dry out befor the next watering. If you look at the media you will find that it is mostly made from chuncks of barch, vulcanic rock and coconut husks. All these materials allow a lot of air to come to the orchid roots. But most of these materials do not absorb and store a lot of water. The best watering method I have found is to submerge the orchid pot in a bowl of water for 15 minutes and then to take it out and let the excess water run off. Watering frequency depends on the temperature and humidity in your house, but once or twice a week should be suffcient. In many loactions tap water contains a lot of minerals and is not recommended for orchid watering. Use clean rain water, filtered drinking water or distilled water instead. Also be careful if you have a house water softening unit installed, some of them put a lot of sodium in the water and orchids do not like that.
You can use a "TDS meter" to measure the mineral content of your water. The reading for water without fertilizer should be below 100 ppm.

Humidity
The best humidity range for Cattleya is between 50 and 60 % relative humidity, but with regular watering they will tolerate lower humidity. To create a better microclimate you can also place trays with moistened pebbles around your plants. They also like to be sprayed with destilled water on a daily basis, but make sure that there is no water in the center of the leafs, since that may promote rot. I use several types of combined temperature and humidity meters, you can find them in my orchid shop.

Fertilizer
Since the potting media contains little nutrients, a weekly fertilizing with dilluted fertilizer is recommended. In most cases a balanced 10-10-10 or 12-12-12 fertilizer at one quarter to one half of the manufacturers recommended strength works well. I usually fertilize for 3 or 4 weeks in a row and then do one submerged watering with clean water without fertilizer. This will flush excess minerals and nutrients away and will prevent an unhealthy build-up of excess nutrients.

Potting
You should repot your Cattleya orchid every two or three years, before the potting media breaks down or accumulates too much minerals. The best time to do this is right after the flowering. More details in the potting section.