Trading up in my building

Perhaps you could sell with the contingency that you are able to find the apartment you want?

Talk to your Super. He/She may be able to quietly help you arrange something like this before anyone in your building even lists an apartment that you may be interested in. You may be able to do something without a broker and save the seller some money for the favor of that owner waiting for you to sell your place. Just a thought.

Sell your apartment first and give yourself 90 days to close with your buyer. Will be plenty of time to buy another apartment.

Definitely worth talking to your super / doormen. Otherwise, send polite letters to owners of the apartment lines in your building you would consider buying, letting them know of your interest, so they can come to you before they list with a broker. I would not put your place on the market until you have secured a new place. You can then arrabe a bridge loan to tide you over until you have sold your unit.

#5 has the best solution. I did that and it worked out for me. good luck!