I have been on my property for 4 years. It has been for sale for one year and under contract twice. It is a roller-coaster, but I have chosen to stay because I love the property and my residents. I am dedicated to maintaining the integrity of the property until the very end.
The current buyer has stated that they would keep me as the manager. They also told me that, if the property were not in good managerial shape, they would not keep a manager.
It's hard to find quality, dedicated employees and unless they have a family member or a very close associate who needs your job, they will likely keep you.
I would stay at least until they have a buyer with approved financing. At that time, I would ask for a retention bonus. I've never heard of that, either.
I have my eyes open, just in case something just as interesting as what I have comes along, but, if not, I'm staying until closing day, whether they hire me or not.
I wouldn't want my resume to reflect I quit by property just because it was for sale. That could make a new employer not consider hiring me, too.
Good luck! Sounds like you are worth a million!!!