Giving the tenant a rent break was a goodwill gesture for the inconvenience.

I mean it’s not a bad thing and it doesn’t mean be super cheap but it will end up costing you much more then any gesture could be worth and won’t add much value. 1000$ dishwashers are nice and may move a tenant in faster theoretically but fixing one can be stupid and people don’t use more then a few settings on it anyways!

See if they are open to providing additional security deposit funds as a gesture of good faith, since the property is clearly getting more use.As a take away, you now know never to rent to pilots again, and/or change your lease in a way to prevent a crash pad (perhaps use that very term in your lease and define it). 

So far you keep it at that and no co-mingling personal and professional relationships because then it can become a slippery slope when some tenants perceive the smallest gesture as a "weakness".

The 1937 version of the book "Think and Grow Rich" (which is excellent) is in the Public Domain, although still somewhat controversially, but basically means that anyone can obtain it for free (but I'm no attorney) and the fact that someone is "giving" it away is a nice gesture, but merely a gimmick.

I could be wrong but I think since the guy specifically wants 500, he just wants some cash for something, it's not totally a question of making the wholesaler do a gesture of good faith...

That is half joking, but a small gesture of your appreciation would make them (and you) feel better.

Well it depends, you can ask and he might do it as a gesture to have you stay longer and he may not even want you to touch anything.

Is there any appropriate gesture of goodwill beyond a card?

It also allows us to give listing agents part of our commission as a bonus and/or goodwill gesture.