"He is with Jen and her kids so much. He wants to have a place he can go to in case this comes to a screeching halt," showbizspy.com quoted a source as saying.
The 25-year-old is desperate to marry the three times married star, but instead of buying her a ring, he suggested they get tattoos affirming their commitment on their ring fingers.
"When he presented her with that idea Jennifer could barely control her laughter," said the source.
Lopez, who started dating Smart after splitting from third husband Marc Anthony, the father of her four-year-old twins Max and Emme, recently admitted she is not ready to tie the knot with her partner, though they are very happy together.