A favorite maxim of Warren Buffett is that the best time to sell is never. While not even the Oracle of Omaha abides by that advice all the time, his track record makes clear that owning a stock for an extra-long time is still a sound approach.

Yet finding the best stocks to buy and hold isn't easy. So to help get you started, we asked three Foolish investors to pick a growth stock that they believe investors would be wise to buy now and hold for the long term. Read on to learn why they like SunPower (NASDAQ:SPWR), salesforce.com (NYSE:CRM), and XPO Logistics (NYSE:XPO).

Rooftop solar panels

Image source: Getty Images.

A solid foundation for profitable expansion

Maxx Chatsko (SunPower): Despite record solar power capacity additions in the United States and globally, many companies in the solar industry have struggled to turn a profit in recent years. That's because solar panel and cell manufacturers have been adapting to new market realities, and transforming themselves into stronger and leaner businesses has not come cheap. But while the last few years have been painful, it's possible investors will be able to look back on them as a crucial turning point for sustainable long-term growth. SunPower might be the most likely solar manufacturer to follow that trajectory.

Management has said the business should return to profitability by the end of 2018. That would be a welcome reprieve for shareholders, as financial flexibility could improve quickly from there. That's because SunPower recently acquired SolarWorld Americas in a move that will give the high-efficiency solar panel manufacturer a production base in the United States. That could prove valuable from a political standpoint in the near term and from a growth standpoint in the longer term.

As SunPower CEO Tom Werner told The Motley Fool's Travis Hoium, the deal aligned the company's strategy with the Trump administration's aim to bolster U.S. manufacturing. The goodwill motion could make it easier to receive an exemption from tariffs imposed on imported solar panels and solar cells SolarWorld produces abroad (products that don't have domestic competition anyway). That alone would provide an additional $50 million in adjusted earnings before interest, taxes, depreciation, and amortization in the second half of 2018 and an additional $100 million in adjusted EBITDA in each full year thereafter.

It could also set the stage for SunPower to earn a sweet subsidy package if it builds a new manufacturing facility in the United States -- something it will need to do to keep pace with industry demand while simultaneously appeasing the current administration. In other words, if management executes on a growth strategy that hinges on profitable (and possibly "fast tracked") manufacturing expansion in the United States, then this $1.1 billion company could be at the beginning of an awesome long-term growth trajectory.

Digital representation of computers being connected to the cloud

Image source: Getty Images.

The future's biggest software company?

Nicholas Rossolillo (Salesforce): Customer relationship management (CRM) software company Salesforce is one of the biggest disruptors in the technology industry. The provider of various cloud-based services to help businesses manage relationships and marketing efforts became the fastest enterprise software company to reach $10 billion in annual sales; it surpassed that milestone last year. Salesforce isn't finished yet, though, setting its sight on an even more ambitious goal.

In the next decade, the goal is to reach $40 billion in revenue, and in the next 15 years it aims to hit $60 billion. That would make Salesforce one of the largest software companies in the world. To get there, though, it's going to need to continue expanding outside of its current wheelhouse of relationship management. Fortunately for investors, founder and CEO Marc Benioff has a proven track record of pulling that off.

In its latest stunt, Salesforce purchased up-and-coming integration software company MuleSoft for $6.5 billion. That's a big price tag, but MuleSoft says businesses will spend hundreds of billions on integrating apps and technology in 2018 alone. And Benioff has promised more exciting announcements to come this fall, including some sort of cryptocurrency and blockchain service. 

Salesforce is growing into more than just a CRM company as its various services are becoming an integral part of big enterprises' technology initiatives. With lofty goals in the years ahead, this stock is worth owning for a while.

XPO Logistics tractor trailer

Image source: XPO Logistics.

Keep on trucking

Rich Duprey (XPO Logistics): One way to give your business a competitive edge is to make your services indispensable to your customers. XPO Logistics is creating an aura of invincibility for itself by making its logistics and transportation services a critical component of the survival of its retail customers.

XPO recently launched XPO Direct, a service that will put small and medium-sized businesses -- and even large ones -- on an equal footing with the retail giants. One of the advantages Walmart and Amazon.com have over their rivals is scale. Their far-flung operations allow them to be within hours of their customers, meaning they can deliver products to a customer's doorstep almost without thinking.

XPO Logistics is leveling the playing field by allowing retailers to use its warehouses, trucks, and logistics services to gain a comparable reach. If a retailer had to build out its own network of stores and distribution centers, the cost would likely be more than it's worth as the capital expenditures would result in higher prices. By sharing its facilities and capabilities, XPO becomes essential to the retailer's survival in the hyper-competitive environment.

That's but one service XPO Logistics has launched and is building on its record of growth. Analysts expect the global intermodal freight transportation market to grow at a compounded annual rate of 16.4% through 2019, hitting $26.2 billion. XPO's first-quarter revenue surged over 18%, with organic growth in the last-mile segment hitting 15%.

At 24 times Wall Street's expected earnings for 2018, XPO Logistics might appear pricey, but it is the industry leader. Considering it trades at only 15 times the free cash flow it produces, while not a bargain-basement stock, it's attractively valued and could be considered as a long-term holding in any portfolio.

John Mackey, CEO of Whole Foods Market, an Amazon subsidiary, is a member of The Motley Fool's board of directors. Rich Duprey has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Amazon and Salesforce.com. The Motley Fool recommends XPO Logistics. The Motley Fool has a disclosure policy.