Here's the ultimate Guide to shopping secondhand in the Upper East Side. Listed in order starting in the low 60s and ending in the 90s.
Goodwill
1st Ave & 61st St
1114 1st Ave., New York, NY 10065
Housing Works
1222 2nd Ave, New York, NY 10065

2nd Street
1282 3rd Ave, New York, NY 10021

Margoth Consignment Shop
218 E 81st St, New York, NY 10028

The Niche Shop
311 E 81st St, New York, NY 10028

Gentleman's Resale
322 E 81st St, New York, NY 10028

Designer Revival
324 E 81st St, New York, NY 10028

Thrift NYC
305 E 84th St, Manhattan, NY 10028

Goodwill
2nd Ave Between 88th and 89th
1704 2nd Ave, New York, NY 10128
Housing Works
1730 2nd Ave, New York, NY 10128
Unique Boutique
1674 3rd Ave, New York, NY 10128