Staying at friend's place in NYC for 1 week -- what's an appropriate level gift?
My husband (32M) is a medical resident, and I (33F) am a medical student -- i.e. we're both living off of his meager salary at the moment, and don't have much disposable income. Husband's best friend CJ (33M) had a long-standing invite for us to visit with him and his soon-to-be-fiance (33F) at their apartment in Brooklyn, NYC. My husband has a vacation week coming up, and we thought doing this visit would be perfect -- we get to meet CJ's fiance, spend time with them, and it'll ease the costs for a vacation. CJ and his fiance happily agreed, and it's happening.
My question is what is an appropriate level gift to get them to express our gratitude for hosting us. They know we're not exactly making bank right now, and I want to be cognizant of that WHILE making sure our gift is appropriate and expressing our sincere thanks. I.e. I don't want to cheap out/take them for granted.
What would be a good amount to spend -- or even something good to get? Thank you in advance for all advice.