How long does it take to buy a co-op, from accepted offer to possession?
Give it three months at least, and more likely four.
Once your offer is accepted, contracts are drawn up and sent from the seller’s attorney to the buyer’s attorney for signature. That could be done in a day, but in real life it ends up taking a week. Then you start hunting for financing, and, if you’re smart, putting together your board package at the same time. Chances are you think you know where your tax returns are until you actually look for them; finding previous bank statements can be easy as signing into a web site, but you might have to order them from the bank by mail, too.
So give yourself four weeks to do all that. (Your board package isn’t officially done till your mortgage financing is approved.) Then you hand in your package, and the managing agent plays with it for a week – xeroxing, running a credit check, maybe vetting your letters of reference.
So now we’re up to six weeks, and your package is just now hitting the desk of co-op board members. Give them three to four weeks to set up a meeting with you (which you really should rearrange your schedule to make) and then allow two weeks to schedule getting everyone around the same conference table for a closing.