there are a lot of very affordable ones these days, from simple Crosley combos like that red one i set up on stage for the troublemaker tour "heartsongs" bit, to portables by Numark, to the usb ones that allow you to record LPs into your computer, to slightly higher end stuff. if you are really serious, consider investing a few hundred into a turntable. good brands to look at are numark, technics, panasonic, marantz, music hall (at that point they are getting pricey though). there arent many stereo shops left that carry any turntables but any Guitar Center will have some models for DJs and they start fairly cheap.
remember you also need an amplifier but if you already have a stereo system in your home then you already have an amp and speakers hopefully.
it gets 1000x more complex and specific if you want to get into it deeper, but thats some basic stuff to start with.