"I just bought a house," Lovato tells PEOPLE of a Mediterranean style home she purchased outside of L.A. "For me to give [that] to my family on my birthday, that was the best present."
Lovato also plans to live on the property, in a house in the backyard. "It's got pretty much everything you could possibly imagine in it," she says. "It's the most beautiful, homey-feeling house. I love it."
And, as a bonus, "the pool has a water slide, which is really cool," she says.
Celebrating her birthday with younger sister Madison de la Garza (of Desperate Housewives) and her Camp Rock 2 costars Joe and Nick Jonas, who were in town to promote the Disney Channel movie which premieres Sept. 3, Lovato and her pals dined at New York's Buddakan – and finished off the evening with a cake.