Alethea Johnson had no idea that her passion for interior design would end up being her career after sharing just one TikTok.

In August, the 29-year-old posted a before-and-after transformation of her sister Athena's dorm room at Morgan State. The video went viral on the app and racked up over 11 million views.

Johnson told CNBC Make It that since going viral on TikTok, she was able to quit her job as a nurse and become an interior designer full-time.

She already has several new clients and rooms she's designing.

"I think that everything happens at the right time," Johnson says. "I'm excited to follow a passion of mine that I've had since I was a young girl and get paid to do what I love."

The viral dorm room makeover cost less than $300

Johnson says redesigning her sister's freshman dorm room was always a given. She had completed a successful makeover of her sister's bedroom at home just the year before.

"She already knew that I was fully capable of giving her something she loved without her being involved. She gave me free reign," Johnson said.

Johnson didn't start with much inspiration or direction for the design, but Athena told her the one thing she didn't want was a colorful room. Johnson decided to stick with a neutral color scheme.

For furniture and décor, Johnson says she turned to Amazon, Dollar Tree, and Home Depot.

It took Johnson, her mother, and her sister about two hours to apply removable wallpaper, install a shelf organizer, and create custom picture frames.

The transformation came in at a little under $300.

"I was actually pretty unhappy with the final result at first," Johnson said. "I changed my mind after seeing how much my sister loved the room."

Johnson added that her sister loved the DIY frames the most and plans on repurposing them during all four years at Morgan State.

"When I FaceTime, she looks very comfortable in her room. It doesn't look or feel like she's somewhere else. It looks like a space she belongs in, and that was my goal," she said.

Since redesigning her sister's half of the room, Johnson revealed she did the roommate's side too.

In total, transforming the entire room cost about $550.

The only guidance she received from the roommate was to stay away from the color pink.

"The inspiration for doing the roommate's side was to spread kindness and the luxurious look," Johnson said. "I knew I was going to a play off the side that was already done while still giving her a unique feel."

Johnson, her mom, and her sister spent about four hours on the second makeover.

"Everyone deserves something special now and again," she said.

"The roommate loved it and insisted on paying, but I wouldn't let her. She thanked me and said her mom couldn't wait to see it."

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