Display of letters/flags on outside of house...

[bevinpiphi]

Check your town ordinances. At the ISU campus/Bloomington-Normal, there's some law limiting placing letters on the house, to the effect of no new Greek letter houses are allowed, but old ones can be bought by different organizations.

edit: I checked the Westbury, NY village site. I see nothing in there that limits you, but check with your landlord/neighborhood organization.