It may be tempting to plunk down money on a boat or a BMW. But does it always make sense?
It all depends on how—and how much—you plan to use them. In some cases, you may be better off renting, or sharing, big-ticket items.
Jeff Rose, certified financial planner and author of "Soldier of Finance," recommends clients run the numbers before making a commitment.
"Figure out, 'Okay, how much am I actually paying per use of this? And does it really work out in my favor?'" says Rose. If not, renting or sharing them with others may make better financial sense.
The good news? Those options are now readily available—and increasingly popular—for everything from smart phones to second homes. We break it down.
Lucy Maher, special to CNBC.com
Ever dream of owning a boat, inviting friends aboard for sunset cocktails and cruising the open sea whenever you want?
You may instead consider dipping your toe into the water by renting.That's because in addition to the six-figure price tag you'll find on most recreational vessels, boat ownership also includes thousands of dollars a year in maintenance charges, docking fees and insurance payments. None of that includes emergency costs.
A better option for most: a membership program like Freedom Boat Club, which gives you access to boats at your home club or reciprocity at a member club for an initiation fee and monthly dues, or a one-time-use service like Boatbound.
Rent if: You enjoy sailing as a pastime, yet aren't sure you'll be able to use the boat regularly for years to come. "I have had so many friends who've bought a boat.They may be hardcore for a year but family life gets busy and all of a sudden their boat's sitting in storage and getting no use," says Rose.
Buy if: You're committed to spending most weekends on your boat—for the next several years.
Gone are the days of a home-run return on your real estate, even in prime vacation spots. "Home prices going up is not a guarantee," says Deacon Hayes, owner and editor of wellkeptwallet.com. "There are ways that you can put that money to work for you and not have the upkeep and cost of a second home."
That includes tapping into any number of short-term real estate rental sites like airbnb , Vacation Rental By Owner or Home Away that let you book on a weekly, monthly or even seasonal basis, or home swapping services like Love Home Swap that act as a go-between for homeowners who want to trade time in their primary residence for time in a residence of one of the other users of the service, no monies traded.
Rent if: Your work or family situation (younger kids with obligations close to home, for example, or older kids with a waning interest in visiting) may result in significant blocks of time you're unable to use your home. The value of the amount of time you will use the home may be less than the most conservative expected return.
Buy if: Your second home is in a place you plan to retire, or you're comfortable with using it as an investment property by renting it during peak times.
Car-sharing services like Zipcar, which charge members a $25 initiation fee plus a per-use charge. The service has been a boon to urbanites looking for a low-cost, hassle-free way to get their hands on a pair of wheels for an hour or two at a time. (Car rental company Enterprise has also introduced its own car-sharing service.) But what about those who need to get around more frequently?
"It's a matter of doing the math," says Rose. Add up the payments plus insurance and parking and it could cost you $600 or $700 a month to own, he says. And that's not factoring in emergency costs. Unless you need a car on a near daily-basis, it may be cheaper to rent a car or join a car-sharing service instead.
Rent if: You only need a car for quarterly trips to the big box store, or the occasional weekend road trip. (Just remember to reserve in advance, since cars can be hard to come by at peak times.)
Buy if: You have children who need frequent ferrying around, a daily commute or live in an area with poor public transportation.
Ever had the thrill of receiving an invitation to a black-tie function vanish when you realize you have to spend hundreds on a dress and bag (or a tux) you'll use once?
Thanks to services like Rent the Runway and Bag, Borrow or Steal, you don't have to. Rent the Runway houses 100,000 designer dresses (one $3,495 Moschino dress rents for $350) and accessories available for four- or eight-day rentals. Bag, Borrow or Steal follows the same model but focuses on monthly handbag rentals. Thread Tread offers a similar service for men, providing a range of clothing options and a personal stylist.
Rent if: You don't like wearing the same thing twice, or you're an adventurous dresser but don't want to stock your closet with items you only use once or twice.
Buy if: The cost of the dress will be amortized by the number of wears.
You can get the latest model smartphone without shelling out hundreds if your carrier offers an early upgrade plan. It works like this: Rather than pay a subsidized price for a phone and a two-year contract, you pay the full price, which is spread out for a set period of time, and get a discount on your monthly bill. You're then able to trade in your phone for a new model down the road.
Rent if: You're regularly enticed to upgrade.
Buy if: You're clutzy and often lose or damage your phone. If your existing model isn't paid off and you break it or it's stolen, you may have to pay the balance due and buy another full-priced phone. While carriers offer protection plans, they add as much as $10 to your monthly bill.
Read MoreThe best insurance for your iPhone
If you're trying to save money by tackling a home-improvement project on your own, you can avoid shelling out big bucks for the power tools you'll likely never use again (and their subsequent storage) by renting them for a daily or weekly charge from big box stores like Home Depot or Lowes.
Rent if: You're doing project-based work and it's a one-time event.
Buy if: You're a hobbyist and will spend most weekends using these tools.