Noise insulation?

Short of asking the couple next door to go make whoopie while you hold your ear to the drywall, you can look up noise complaints on the 311 database. Also Google the building and its management. You can ask here too

PS, in general a building constricted as a single family (brownstone) will have less insulation between floors than a multifamily.

I like to check floor plans if for example my bedroom is adjacent to a neighbors living room, bedroom or only exterior walls.

Walls you can address by adding a layer of sheet rock. Ceiling in most cases can really be addressed by the neighbor following the carpeting rule of nyc multi family. Most would follow to some extent and there are always some who would refuse to put any carpeting. Then you have city noise for which you can check that windows are double pane. In general pre-wars have better insulation vs post war till 1980s.

https://streeteasy.com/blog/80-percent-rule-carpet-floor-covering/

@300 - back in my condo rental days I had some pretty bad layouts
One, our bedroom was adjacent to the neighbors living room, specifically where they had a wall mounted tv.
They kept weird hours and had addiction issues.
Don’t think drywall would have done much.

The other one we definitely got to hear a lot of neighbor sex. So there’s that.

An additional layer of normal drywall is usually fine. There are drywall available with 2-3x better sound resistant capabilities for marginal more price difference to total construction cost.

Good to know about extra sheetrock if necessary - tx

And if you can get access to the cavity between walls, batt insulation (even better: spray foam) will help noise transmission as well. (I'm faintly surprised that spray foam isn't that popular in new high rise construction - either on exterior or interior walls).

@aaron thanks - sounds like a good contracter could help with that. I gather you'll never get a board to say 'yes you can do this' in advance :/ and have read even asking/mentioning alterations to a board risks a deal rejection. A friend in a lawsuit with his board over a modification he wants to make and it's dragging on

There have been a number of cases where after someone does a renovation the neighbors have huge noise problems (one involving a famous model/actress and a multimillion $ renovation). So even if there's no noise issue when you buy....