Jamie Lynn Spears is getting ready for her baby

Jamie Lynn Spears and her fiancé Casey Aldridge are in full-on nesting mode.

The parents-to-be, who recently purchased their first home together in Liberty, Mississippi, are preparing for the imminent birth of their child, sources tell PEOPLE.

"They're very happy," says a source. "They're a fun little couple."

To get settled in their new home, Spears, 17, and Aldridge, 19, recently had furniture – including an elaborately carved four-poster king-size canopy bed, a leather recliner, and a leather sofa – delivered to the house.

Spears's mom, Lynne, is helping her daughter decorate the nursery, with the color scheme of pink, brown, and "silver-green," says an insider.

Spears, who is due to give birth soon, has been keeping a low profile as she readies the new house for her baby. The five-acre Liberty property is already equipped with a barn and studio, which was formerly used as a hair salon.

One new neighbor, who has already offered to babysit, says, "They're just a sweet little old couple."

Spears and Aldridge, who got engaged in March, plan to wed after the baby is born.

Source: People

- Had to post that picture of the Jamie Lynn Spears doll.