I guess by asking this question, you're relatively new to vinyl?
There are some kits out there, but IMHO a kit is not worth it, & since there are so few to be seen, I think manufacturers have realised that as well.
The main cost in turntables is the components - plinth, motor, bearing, platter, arm, etc. Putting those together is a minimal cost.
There are some good budget turntables from the likes of Pro-Ject, Rega, U-Turn Audio that will sound better than the average 'consumer' plastic affair you will see in big electronics stores these days. (guess it's a good sign though, that at least they HAVE turntables)
Also, there are fine vintage turntables to be had, some for not much money. And there is a lot of business in aftermarket parts for many models, which ends being somewhat like a kit anyway when you start replacing parts.
Hope that helps.