The MapQuest Nominatim service does not appear to be providing house number details in the results. The same search request to the openstreetmaps nominatim service does. Here's the examples:
http://open.mapquestapi.com/nominatim/v1/reverse.php?key=<YOUR KEY HERE>&format=json&lat=39.52101130038007&lon=-119.80317803952164
returns:
{"place_id":"2602606390","licence":"Data \u00a9 OpenStreetMap contributors, ODbL 1.0. http:\/\/www.openstreetmap.org\/copyright","osm_type":"way","osm_id":"302981220","lat":"39.52125","lon":"-119.8031728","display_name":"South Wells Avenue, Reno, Washoe County, Nevada, 89505, United States of America","address":{"road":"South Wells Avenue","city":"Reno","county":"Washoe County","state":"Nevada","postcode":"89505","country":"United States of America","country_code":"us"}}
and http://nominatim.openstreetmap.org/reverse?format=json&lat=39.5210113003...
returns:
{"place_id":"1577238415","licence":"Data © OpenStreetMap contributors, ODbL 1.0. http:\/\/www.openstreetmap.org\/copyright","lat":"39.5210056938775","lon":"-119.803279","display_name":"517, South Wells Avenue, Reno, Washoe County, Nevada, 89502, United States of America","address":{"house_number":"517","road":"South Wells Avenue","city":"Reno","county":"Washoe County","state":"Nevada","postcode":"89502","country":"United States of America","country_code":"us"}}
Not sure if there are other parameters that could be provided in the mapquest API to return the house number information.
The Nominatim search results are very inconsistent:
These make it hard to parse the data. House numbers are a must.