The woman stayed for more than an hour, despite Mr Hardwick insisting multiple times that he was not interested in the $3000 machine.
He received the free gift after the woman left - plastic storage containers with lids. Mr Hardwick said he felt pressured.
"I don't like being hassled like that," he said.
Mr Hardwick said the free gift was "something you could pick up from the dollar store".
HCC Ltd owner Richard Masih said he stood by his sales representative's sale techniques.
"We are promoting our product. If they like the machine, that's great. If they don't like the machine, they get the free gift anyway, so that's great," he said.
The cards left in letterboxes state "the purpose of this promotion is to obtain business" and that business is to sell vacuum cleaners.
The brand of machines Mr Masih and his team are selling, Envirotech vacuum cleaners, was ranked among the worst vacuum cleaners on the market by Consumer in a February 2012 test.
Ms Chetwin said Consumer had found Envirotech machines to be poor. She suggested that people "slam your door in their face if you have to."
She also advised any elderly residents to always have a family member present when inviting a sales representative into their homes.
Daphne Pawson, also from Tikipunga, said she was curious when she came across the free gift card and told the operator the saleswoman could come around that evening.
"When the girl arrived, it was clear she had no sales experience," Mrs Pawson said.
She said when the pitch was over it was 9.15pm, and her husband had tried to cut to the chase on multiple occasions, asking the price of the machine and saying they weren't interested.
"I even asked for a brochure to tell my friends, but she didn't have anything."