What do you plan on getting, specifically?
The non-american killifish and kin usually likes shallow warm water with pebbles or fine sand as substrate. Lots of live food are a must to get them to breed successfully.
They are generally aggressive so keeping them in a species tank is ideal. There certain exceptions to some species though.
Some salt added to their water is beneficial but not to the point that it turns brackish. Captive bred killifish normally does well with neutral to alkaline water