Living on a boat means that the Trains can take their home wherever they go. Francesca Spidalieri Three years ago, Sam Train, a naval officer stationed in Newport, Rhode Island, asked his wife, Francesca Spidalieri, if she'd be willing to live on a boat.

"She said 'Sure,'" he recalls. "I was flabbergasted."

But it made perfect sense to Francesca, since the couple would be moving every few years.

"At least this way, we get to own something and bring our home with us," she explains.

They ended up buying a pre-owned 40' Catalina cruiser for $150,000, with mortgage payments of about $800 a month.

For two years, they lived on board during the summer, then moved to a rental apartment in winter.

But at the end of 2013, they found out that they'd be moving to San Diego, where the climate would be mild enough to live on the boat year round.

"I did the math and figured out that we'd save $50,000 over three years, if we lived on board instead of renting an apartment in San Diego and leaving the boat on the East Coast," Sam says.

So they used the Navy's relocation allowance to cover the cost of having the boat shipped from Rhode Island to California.

The Trains' 40' Catalina has two bedrooms and a full kitchen on board. Francesca Spidalieri

A year later, they still think that it was the right choice. In an average month, it costs them around $2,200 to live on the boat. By comparison, they would spend $2,500 to $3,000 to rent an apartment in a similar area of San Diego, and still be paying the boat's mortgage on top of that.

Keeping the boat at a marina is the largest expense besides the mortgage. Francesca Spidalieri Their largest expense is paying to keep the boat at a marina, which costs $1,050 a month, including the $250 "live aboard" fee.

That covers utilities such as water and electricity, and also allows them to keep their cars in the parking lot, use the pool and laundry facilities, and receive mail and packages there.

Though there are other expenses that they wouldn't have if they lived in an apartment, the costs are minimal.

For $25, a pumpout boat empties their sewage tank, which usually needs to be done once a week.

Sam maintains the boat's mechanical systems himself, but the couple hires a professional to wash and wax the boat's exterior once a month, which costs $80. Every six months, they pay a diver $50 to clean the bottom.

Since they're living in approximately 300 square feet of space, renting a storage unit for $100 a month is a non-negotiable expense. In addition to the extra bedding and towels that they use when guests come, it also holds the majority of their clothing, serving as a giant walk-in closet.

The couple also budgets $1,000 a year for any unexpected maintenance costs that may come up. "It's like a car, where you don’t spend anything for a while and then you spend a ton of money," Sam explains.

Sharing the boat with a baby has been a learning process. Francesa Spidalieri

Sam and Francesca had their first child in August, and they admit that sharing an already-tiny space with a baby has been a learning process.

But they're better suited to it than most.

Francesca grew up in Italy, and says that the boat is much more luxurious then any of the tiny apartments that she rented there as a student.

And Sam has gotten used to living in a small space on board a ship while he's been in the Navy.

Living on a boat is an experiment in making do with less. Francesca Spidalieri

The experience has forced them to limit the number of things that they own, and taught them that they can deal with minor inconveniences like not having their own laundry machines.

"You can't take the American dream of a big house, big yard, and picket fence, and easily wrap it into a small space like a boat," Sam says.

"You have to give up a lot of stuff."

"The idea of making do with less is something that I hope we can take with us, wherever we go next," Francesca adds. "Even if it is a house."