
a Non-Human

is a cost as it comes immediately before the colon (rulebook, page 4). You can only pay costs with cards you control (pages 2 and 4).
To a certain extent though, costs are one area we're going to look to clarify/improve in the rulebook, as a few concepts are either assumed the player base will know, or could be explained better.
One instance of the former is that costs are also self-referential. Take Liach, T'zen and Giiar for instance. Her ability is:

- Jettison: Change the target of an

or cancel an

.
We don't actually say anywhere that "Jettison" refers to the card itself. The self-referential default in absence of other identified cards is a common practice, but not one we should have assumed our player base would know.
Alien Quarter Market falls under this as well. It's costs are:

,

non-Human

:
So the first

requires you to

Alien Quarter Market.