How do you say "preferences" as opposed to "demands"?
When asking for preference, you can use 愿意 to indicate what you are willing/prefer to do, or ask what he is willing/prefers to do. You can also use 想 to ask/indicate what he/you wish(es) or is thinking of (doing/wanting).

E.g., 你愿意租什么样的公寓(呀)? 我愿意找个有两层的公寓. (What kind of apartment/flat would you like to rent? I would like to find a two-story apartment/flat.)

You can use 必须 indicate what you must have or have happen. 

E.g., 那桌子必须是红色的. (That table must be red.) / 你必须把他带回来. (You must bring him back.) / 那公寓必须有一个浴缸. (That apartment/flat mush have a bathtub.)

If you want to indicate that an alternative something also good/fine, but not would not be your top choice, you can use 也好, 也可以, or 也行.

E.g., 我喜欢(吃)香草(味的)冰淇淋, 不过草莓(味的)也行. (I like [to eat] vanilla [flavored] ice cream, but strawberry [flavored] is fine as well/also good.)