You shouldn't have to keep a close eye on your investments. If you find solid stocks to buy, you can leave them in your portfolio and simply wait for their operations to grow and become larger over time, leading to potentially great returns in the long run.

Three stocks that look promising today are Regeneron Pharmaceuticals (REGN -0.62%), Carnival Corp. (CCL 1.15%), and Alphabet (GOOG -0.19%) (GOOGL -0.17%). These stocks provide good value for investors today, and buying them before they soar even higher in 2024 could be a great move for investors to make right now.

1. Regeneron Pharmaceuticals

Biotech company Regeneron Pharmaceuticals is a growing business that has plenty of potential to get even bigger in the years ahead. What makes it an attractive long-term play is that it generates ample revenue and free cash flow today due to Eylea, its treatment for wet age-related macular degeneration, and multiple collaboration agreements with top pharma companies, including Sanofi and Bayer. This includes the multibillion-dollar asset it has in Dupixent, a treatment for eczema, which it has been developing with Sanofi. At its peak, it could generate $20 billion in revenue.

Over the past three years, Regeneron has accumulated free cash flow totaling $11.9 billion. That can be incredibly valuable for a growing business that needs money to continue to get larger. Plus, the business is already hugely profitable, with Regeneron enjoying profit margins of 30% over the trailing 12 months. Strong financials can provide the business with lots of runway to get even bigger in the long run.

The healthcare stock is trading at just under 20 times its estimated future earnings, which is in line with the S&P 500 average. But with solid fundamentals and more opportunities to get even bigger (the company has more than 35 active trials ongoing), now can be an excellent time to buy the stock while it's still a relatively cheap buy.

2. Carnival Corp.

Cruise ship operator Carnival has been recovering nicely this year. However, investors remain hesitant to buy shares of the business, which could prove to be a mistake. At a forward price-to-earnings multiple of 17, the stock offers good value to investors. The pandemic, lockdowns, and the general bad press that followed cruise ships over the past few years resulted in Carnival Corp. going from a stock that was trading at more than $40 a share in early 2020 to now struggling to stay above the $20 mark.

Carnival's results have been showing signs of improvement, with the company reporting a positive operating profit in its two most recent quarters. For the period ended Aug. 31, its profit was just under $1.1 billion. Over the past three quarters, it has also generated positive operating cash flow.

The business still faces challenges, as it has $29.5 billion in long-term debt on its books. But it has been reducing that, and with the company's recent financial performance looking much stronger, there's no reason that it can't continue to come down in future quarters. Carnival is one of the more promising stocks to own while its valuation is down. And given its strong customer base and focus on retirees, it may be a resilient investment to own, even if there is a slowdown in leisure travel in 2024.

Carnival is a great growth stock to own, and now can be an excellent time for investors to load up on its shares.

3. Alphabet

This year has been a strong one for tech giant Alphabet. Up over 50% year to date, it has been part of the "Magnificent Seven," which have been helping the S&P 500 perform well in 2023. And yet, the stock still isn't overly expensive as it is trading at 20 times its future profits.

The company behind Google and YouTube is also a hot buy due to its chatbot, Bard. And the momentum could pick up significantly now that the company has unveiled its new artificial intelligence (AI) model, Gemini. The model will help Bard become better and more competitive with OpenAI's ChatGPT-4. The company is also using a smaller version, the Gemini Nano, in its new Pixel 8 phones, which allow people to use AI to help make enhancements and changes to images. AI-powered products and services are still in their early stages, but Alphabet looks to be a promising company in this realm.

Alphabet has generated more than $60 billion in free cash flow in each of the past two years, and that's a good example of why it may have plenty of resources at its disposal to invest heavily in AI.

The good news for investors is that it's not too late to invest in this magnificent business. The stock isn't overpriced right now, and shares of Alphabet could soar even higher in the future.