Regardless of whether you think a market crash will happen today, tomorrow, or a year from now, it is never a bad idea to be prepared. And a good way to do that is to keep track of quality stocks that are simply too expensive to be investing in right now. That way, if there is a crash, you can act quickly and not miss out on deals that may not last for long.

Three stocks currently on my watchlist that I would love to grab if there is a correction include Planet 13 Holdings (PLNH.F -3.75%)Starbucks (SBUX -2.99%), and Square (SQ -1.07%). Their valuations are high right now, but if they come down, they could be some of the best stocks to buy for the long term.

Woman uses her mobile phone to order at a coffee shop.

Image source: Getty Images

1. Planet 13

Are you looking for a stock that will boom in a post-pandemic world? How about one that is in a high-growth industry? Planet 13 checks both those boxes. The Las Vegas-based cannabis producer has enormous potential. Although it has been delivering strong results amid the pandemic, as governments lift COVID-19 restrictions, the sky is only the limit for the pot stock. I only hope that it drops in value before that happens.

Over the past 12 months, its shares are up a ridiculous 709%, blowing past the S&P 500, which has risen 60% during that time. And it is easy to see why investors are excited. Voters in four states chose to legalize marijuana for recreational use in November 2020, and more markets could open up soon, including New York, which is taking a serious look at legalization this year. The growing optimism surrounding legalization (including at the federal level) has many pot stocks doing well; the Horizons Marijuana Life Sciences ETF has climbed nearly 155% in the past 12 months.

Planet 13 last reported earnings on Nov. 24, 2020, when sales of $22.8 million for the period ending Sept. 30, 2020, rose 36.5% year over year. But with travel in and around the U.S. down due to the pandemic, the company can generate a whole lot more growth once governments lift restrictions. Its dispensary in Las Vegas, called the "Superstore," is 112,000 square feet in size and features many other businesses; the company hopes it will become a tourist attraction that brings in more than just cannabis consumers. Planet 13 is planning to launch a second location in Santa Ana, California, later this year. At 55,000 square feet, it won't be nearly as big as the Las Vegas location, but it will be strategic, just 10 minutes away from Disneyland.

The only thing that keeps me from buying the stock is its price. Its price-to-sales (P/S) ratio (this is used rather than earnings as the company remains unprofitable) is around 15 -- well above the 4.6 times sales that the average stock on the Horizons Marijuana Life Sciences ETF trades at. Planet 13 is too pricey a buy right now, but that could change if there is a market crash.

2. Starbucks

Starbucks is a great buy-and-forget stock because of the company's cult following and strong, consistent sales numbers. Even though COVID-19 restrictions and lockdowns have hindered its business over the past year, Starbucks is showing resilience. On Jan. 26, the company released its first-quarter results for fiscal 2021, and comparable-store sales in the U.S. were down a modest 5% for the period ending Dec. 27, 2020.

Aside from one bad period in 2020 for the third quarter ending June 28, 2020, where sales of $4.2 billion declined by 38% year over year (due to pandemic-related lockdowns), the company's sales have stayed at or around $6 billion in revenue in each period during the pandemic. And its profit margins have also remained relatively steady at 5% or better, although they're below the 10%-or-higher margins Starbucks has enjoyed in previous years. Still, given the headwinds from COVID-19 (e.g. supply shortages and higher prices), it's not too surprising that the company's bottom line wasn't as strong in 2020.

Starbucks is optimistic for the current fiscal year (which ends in September), anticipating that global comparable-store sales will grow at a rate of 18% to 23%, and that in the U.S. and Americas they will rise between 17% and 22%. It is projecting per-share profits as high as $2.62 (including a $0.10 impact from a 53rd week). That would indicate a near-complete recovery from the $2.92 earnings per share Starbucks reported in fiscal 2019.

In the past 12 months, shares of Starbucks have risen more than 50%. And with a forward price-to-earnings (P/E) multiple of 38, this is a bit of a steep price to pay right now given that the average stock in the SPDR S&P 500 ETF Trust trades at only 28 times earnings. Starbucks is a great stock, but the price isn't right to buy it just yet.

3. Square

Square has a great business model for an era in which people are trying to avoid holding cash due to the pandemic. The company's terminals make it easy to transact using debit and credit cards, without the need to rent a costly device from a bank. Anyone can become a merchant without the hassle of worrying about paying monthly fees even if they aren't using the devices. And the need for digital payments is here to stay, with the pandemic likely accelerating that transition. PayPal CEO Dan Schulman says that companies need to offer digital payments, as they have moved from "being a nice-to-have capability to a must-have essential service."

But what's driving Square's growth right now is the rising popularity of Bitcoin (BTC -2.19%). The digital currency has skyrocketed more than 1,000% in the past year, and Square allows users to buy the crypto through its cash app. In 2020, Square generated $4.6 billion in Bitcoin-related revenue. Not only was that nearly nine times higher than 2019's tally of $516 million, but it now accounts for nearly half of the company's sales, which totaled $9.5 billion last year. In 2019, Bitcoin sales represented just 11% of Square's top line. Outside of Bitcoin, Square generated $4.9 billion in sales in 2020, which was a 17% improvement from the previous year. 

The exposure to Bitcoin can both be a blessing and a curse for Square, because if the digital currency crashes as it did in 2018, Square could go along with it. But if you are bullish on crypto, it's a great way to tap into that potential growth. Either way, you still might want to wait to buy Square, as it trades at a forward P/E of more than 190, an egregious valuation regardless of the industry you are investing in. Hype has clearly helped Square skyrocket to an outrageous price, and as much as I would like to buy the stock today, it is just out of my comfort zone until another dip comes.