Cats don't usually get fleas unless they are going outside, and around tall grass or tall weeds - such as in a field. We had cats who would go in and out for many years and they did not get fleas, even without any flea treatments. The only time we got fleas was when they were transferred from a relative's animal.
If you get a kitten, you should then inspect the kitten by using a metal flea comb. If you see fleas stuck in the comb, the kitten has fleas. You can also look at the skin. A cat or kitten with fleas will usually have what looks like "dirt" on the skin.
If the kitten has fleas, put him in the bathroom until fully treated (that is the best place for a kitten who is less than 12 weeks, anyway). Either give the kitten a bath with Dawn dish soap, or give the kitten Capstar, or its generic. You can get Capstar online. Capstar will kill the fleas right away. Dawn dish soap will kill the fleas, too. A metal flea comb works but must be repeated daily until no signs of fleas show.
Repeat dish soap bath in one week. Repeat Capstar each 3 days or so for two or three weeks. Capstar is safer than the monthly flea treatments. ONLY use these products by package directions. NEVER use on a small or young kitten. Always read what the package says. DO NOT use flea products from the store such as Hartz flea products - they are not safe.
Monthly flea treatments are not necessary, unless your house is already infested with fleas. In that case, sprinkle the carpeting with baking soda and leave on for 24 hours; vacuum; repeat in one week.