The Season 14 The Bachelorette star and "Bachelor Happy Hour" podcast host continued, "Let's fill this home with so many laughs, meals, memories, and maybe a couple babies."
In the photos, Becca and Thomas posed in front of a giant "SOLD" sign.
Thomas posted similar images on his own Instagram account and wrote alongside them, "So, got a new forever roommate today. Please don't kill me when I tear up the house over the next 3 months #LiveLaughBoops #Home."
Congratulatory messages poured in from Bachelor Nation including Abigail Heringer, who wrote, "[Noah Erb] and I can't wait to crash the guest room!!"
Earlier this summer, Becca and Thomas discussed on multiple podcasts how they were house hunting but not rushing into buying one. They were also planning at the time to live in New York City for a few months this year before settling down in San Diego, CA, long-term.
As far as their upcoming wedding goes, Becca told Entertainment Tonight last month how she's not really interested in televising her wedding. Becca said she'd like to keep her nuptials "more intimate and personal" with Thomas.
"I can never say no because every time I say, 'No, definitely not,' something ends up happening," Becca joked with ET about a televised wedding, "so we'll see, but I don't think [a TV wedding] is in the cards for us."
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Becca also previously noted how two televised -- and broken -- engagements to The Bachelor Season 22 star Arie Luyendyk Jr. and The Bachelorette 14 winner Garrett Yrigoyen is "enough" for her.
Becca said she and Thomas already "have an outline" for their big day.
"We just want to have a big party, a celebration, that probably won't be traditional in any sense," Becca said.
"We're just enjoying this moment, and living in the engagement bliss, and enjoying being able to say 'fiance.' I'm sure very soon, in probably the next couple months, we'll start to actually plan and sit down and figure out what it will all look like."
She added, "I'm not a planner. I just hate to plan anything and so I'm like, 'Thomas, you can take the reins here.'"
Becca told Access Hollywood last month how she thinks Thomas "is still planning to do something special" for her and will pop the question, resulting in two engagements for this couple.
Becca said during an early May appearance on her "Bachelor Happy Hour" podcast that Thomas is "very well aware" of the fact she would like her third engagement to be personal and intimate with nothing "extravagant" and no "big scene."
Thomas -- who previously noted how Becca wants an elongated cushion-cut diamond ring and he could see himself proposing by the end of 2022 -- recently suggested he may have already purchased a ring for Becca.
Thomas teased on an April episode of the "Click Bait with Bachelor Nation" podcast, "Am I aware if I have one in a safety lockbox in my bedroom? I don't know, time will tell. We'll have to find that one out later on this year."
He also confirmed of the potential marriage proposal, "I don't have a full plan yet, but I know it's going to be small and intimate. There will be a camera. I'll have a photographer, but the last thing that I want for Becca is to have another grand spectacle."
Before meeting Thomas, Becca had her heart broken by Arie shortly after they filmed The Bachelor's 22nd season. The finale, which aired in early 2018, featured Arie getting down on one knee and popping the question.
But Arie unexpectedly dumped Becca and called off their engagement because he realized he was still in love with his runner-up, Lauren Burnham, who is now his wife and the mother of his three children.
Becca also had a very public breakup with Garrett Yrigoyen in Fall 2020. Becca and Garrett split just about two years after Garrett's marriage proposal aired on The Bachelorette's fourteenth season.
Becca is hoping the third time will be the charm with Thomas, whom she said is her first fiance she has truly wanted to marry.
Thomas told Hollywood Life in November 2021 that he was pretty sold on marrying Becca because they have "the most healthy, normal relationship"
During an October episode of the "Talking It Out with Bachelor Nation" podcast, Thomas gushed of Becca, "I don't want to spend my life with anybody else... I wouldn't want to wake up next to anybody else."
On Bachelor in Paradise's seventh-season finale, Becca was shown breaking up with Thomas and crushing his heart before overnight Fantasy Suite dates because, despite having "an incredible start" to a relationship, Becca didn't want to leave The Bachelor franchise for the third time with a man unless she knew everything about him, including how he'd face adversity and real-life challenges.
However, the finale concluded with an update on Becca and Thomas' relationship, revealing how they had reunited after filming ended and were dating, "happy and in love."
Becca said she met up with Thomas in San Diego and they picked up right where they had left off, and Thomas told Hollywood Life that he had no hesitation or reservations about giving Becca another chance.
Becca also boasted about how Thomas is different from her past relationships because he's so passionate about a life with her and was prepared to fight "tooth and nail" to save their romance.
"He is so supportive and he's just funny and quirky in the cutest ways. Everything about him, I just felt safe with, unlike anything I had in the past. I was just like, 'This guy is my guy,'" Becca gushed.
Becca even told her mother last year, not long after Paradise ended, that she wanted to marry Thomas, who originally competed on Katie Thurston's season of The Bachelorette in early 2021.
Becca admitted at the time, "It's the first time I've ever actually said that out loud."