Accessory Hacks vs True Multiplex Investment

[Duane Ward]

Some of you may have seen this post before because i accidentally posted it in the general one instead of here. 

I've been doing research after seeing so many accessory apartments listed as multifamilies in long island. After understanding the nuances and history more, I'm wondering, are there certain towns or hamlets in long island that only allow accessories vs duplexes in nassau and suffolk? Does anybody know which areas of long island may not allow duplexes or number-plexes below a 6-plex? We're essentially trying to rule out anyplace that only allows accessories to help narrow our investment property search.

Also aside from certain key words like accessory apt and number of meters, what are some other tricks to spoting a property that is a true multi family investment opportunity vs an accessory listed as a multi family?