Septic tank

What would be the best size and type of septic tank for a household of 8 if it's only for the kitchen sink? We won't need it for anything else, and I don't want to spend a ton on something that I don't need to.

Hi Cassie, welcome to permies!  

First off, your local or state government may have some rules about septic sizing (mine certainly does).  

Secondly, is it a tank that is connected to a septic drain field or leach field?  Or is it just a tank that needs to be pumped out as it fills up?

I'm guessing you could get away with the smallest one they make.  I'm not sure what that is but I'm guessing something like 500 gallons.