He said when a person texts, one of the company's agents calls the next day.
"We'd call and say, 'Have you got all the information you need? Is there anything else we can do to assist you?' And people will say, 'Yes, we're looking for something else'. We can provide more information."
If a potential buyer contacted the agency, bypassing the text, they would provide the address, he said.
"A salesperson can qualify a customer's interest and provide other useful information about that property, other properties we're selling, and how else we can be of service."
The 50c fee for the text was kept by the service provider, he said.
The vendors were aware of "all the elements in our marketing".
The Real Estate Agents Authority is unsure whether the practice breaches any rules because the issue has not been tested. But if vendors were unaware of the marketing approach and feared viewings of their property might be restricted, they may have cause for a complaint, a spokesman said.
Mike McColl of Newmarket's Evolution Realty said he was shocked when he saw the listings.
"I couldn't believe that one ... That's not acting in the vendor's best interest ... If you're acting on behalf of the vendor, you make it easy for buyers."
He said in his own marketing material he asked house-hunters to text him if they wanted a price range on a home, and he called them back, but he wouldn't withhold an address.
Robyn Forryan, of Auckland consultancy Property Magic, said she had not seen the practice before.
Text for the address
• Napier real estate agency Cox Partners Estate Agents includes the following message on all its listings: "For address TXT [listing number] to 842. You will receive an instant text reply with the address and other details about the property. Texts cost 50c, please check with the bill payer."
• The Herald texted for one listing and received the following: "29 Clyde Rd, Bluff Hill - 10483, price $765,000, 5bdr, 4bth, 4gge, rates $2931, freehold, floor 292m2, land 1258m2, views, call Cox Partners (06) 835-4321 anytime".