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When Nicole Nuss saw the little yellow house in Vallejo, with its white picket fence and huge yard for her beloved dog, she knew she wanted to live there more than she’d ever wanted anything.

But in a real estate market where homes fly off the shelf in days and buyers compete with cash offers that are tens of thousands of dollars over asking price, the 38-year-old owner of Cinnaholic bakery in Berkeley worried she didn’t stand a chance. So at the suggestion of her real estate agent, Nuss did something that, at the time, she thought was a bit weird: She wrote the seller a “love letter.”

The time-honored practice, in which prospective buyers pour their hearts out while simultaneously trying to flatter the sellers, has become an unofficial requirement of Bay Area real estate transactions.

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“I am writing to say I have fallen absolutely in love with your cottage and would be beyond honored to call it my first on-my-own home,” Nuss wrote this past summer in a two-page note that included a photo of her giving her dog, Bailey, a belly rub.

It worked. The seller accepted Nuss’ $325,000 offer, even though it wasn’t the highest one on the table.

In today’s super-charged market, these love letters are becoming increasingly common as wannabe buyers desperately try to stand out from the hordes of people fighting over the Bay Area’s few available homes.

“You have to write,” said Oakland and Berkeley-based real estate agent Debra Alber. “If you don’t write them, it kind of shows the sellers that you don’t care.”

And to land a home in this red-hot market, you have to care.

In January, 96 percent of homes sold in Santa Clara County and 89 percent of homes sold in Alameda County received multiple offers, according to Redfin. In San Francisco, 86 percent did. And selling for more than the listing price has become the norm. In Oakland, 75 percent of homes sold for more than asking last year with a median of $51,000 over the listed price, according to Zillow. In San Jose, 72 percent of homes sold above their asking price with a median of $50,000 over, while in San Francisco 69 percent sold above asking with a median of $155,000 over.

Even though an over-the-top offer generally wins out, especially if it’s all cash, in situations where the money is close, a personal letter can help the seller make an otherwise tough decision. That’s because selling a home where a family has lived for years and made countless memories is an emotional process, said San Jose-based real estate agent Mike Gaines.

“A lot of sellers want their homes to go to families and to be treated the same way that they treated the home,” he said.

Writing the perfect letter has evolved into an art form, with how-to guides offered by real estate websites such as Trulia and Redfin. Some prospective buyers use special formatting and computer graphics to make their letters stand out. Others record video testimonials.

Kevin Cole, president of the Santa Clara County Association of Realtors, remembers one offer that included an ultrasound photo of the pregnant buyer’s unborn child. While representing a client selling a four-bedroom, two-bath home in Campbell, Gaines recently received an offer that included a letter written by a buyer’s kid on yellow construction paper.

“Your house is beautiful and neat,” said the letter, written in colorful, childish handwriting. “We want to know whether we could or could not buy this house.”

When writing love letters, Oakland-based realtor Kerri Naslund-Monday, who represented Nuss when she bought the little yellow house in Vallejo, recommends clients include specific details they appreciate about the house. They also should share personal information about themselves and their families.

“If they’ve ever rescued an animal, that should go in there,” Naslund-Monday said. “Anything that could potentially make the seller say, ‘Oh these are really great people’.”

Some light social media stalking can uncover a seller’s favorite sports team or vacation destination, agents say, which can help buyers forge a connection. One of Naslund-Monday’s clients tried to bond with a seller over the fact that both were dog lovers. The buyer took a photo of the seller’s dog from Facebook, had it turned into a caricature and attached it to the offer.

Other clients use their professional connections to sweeten their offers, Naslund-Monday said. One offered the seller Blue Bottle coffee delivered to their door every two weeks for the next year. Another offered the seller a lifetime discount at a garden store in Berkeley. Others have offered to pay a portion of the selling agent’s commission.

But there are risks in attempting to turn the buyer-seller relationship into something more personal. A love letter that includes photos of the potential buyers and their family could invite discrimination based on race or other characteristics — even though it is illegal under state law. That’s why realtor America Foy discourages his clients from sending photos or using their last names and other information that’s searchable on social media.

Tess Coyne, who sold Nuss her dream house in Vallejo, said the love letter made all the difference. Coyne, 61, received 11 offers for the 700-square-foot house, eight of which came with letters. Nuss’ letter stood out in its level of personal detail — she wrote about her family and her upbringing in Pennsylvania.

“It was quite revealing,” Coyne said. “So I felt like I knew something about her before I even met her.”

The yellow house was the first that Coyne, a real estate investor, bought after moving to California from Alaska. She put a lot of care into fixing it up before renting it out, including choosing the perfect shade of yellow for the exterior. So when Coyne decided to sell as she wound down her real estate business, she wanted a buyer who appreciated it. That buyer was Nuss.

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“You could just tell how much she wanted it, from the letter,” Coyne said.

Nuss wanted the house so much partly because she had long ago promised a yard to her 17-year-old dog, Bailey. Once Nuss fulfilled that promise, letting Bailey take a test romp while she picked up the key, the senior dog died right before Nuss moved in. Now Bailey is memorialized, standing in her yard, in a portrait Nuss plans to hang on her wall.

That love for her pets came through in the love letters Nuss wrote to Coyne — one with her initial offer, and a second when she became a finalist.

“They may have been corny,” Nuss said. “They probably were — I’m a little bit corny. But they were just completely honest.”