Retail investors can expect access to this summer’s most anticipated initial public offering — and possibly the largest ever. But you may not be able to buy all the shares you want, experts say, and it’s not a smart move for all investors.

Elon Musk’s rocket and satellite company SpaceX said that a portion of its shares in its offering would be sold directly through online brokerages, including Robinhood, Fidelity and Charles Schwab, according to a prospectus released Wednesday by the Securities and Exchange Commission.

The firm is reportedly looking to raise up to $75 billion in a June offering, which would make it by far the largest U.S. debut of all time, a title currently held by Alibaba’s $22 billion offering in 2014.

In general, investors have reason to be enthusiastic about getting in on the proverbial ground floor of a newly public company. From 1980 through 2025, stocks have popped by an average of 19% from their offering price on the first day of trading, according to data from Jay Ritter, director of the IPO initiative at the University of Florida.

Offering-priced shares aren’t typically available to retail investors, though, Ritter says, particularly for “hot” IPOs where he estimates 95% of shares go to institutional investors, such as major Wall Street banks. Across all IPOs, Fidelity pegs the split between institutional and retail investors at 90/10.

The filing this week indicates SpaceX may be planning to buck this trend. The company may make as much as 30% of shares available to retail investors, according to a March report from Reuters.

Under certain circumstances, experts say, there is short-term money to be made investing at the very beginning of an IPO. But because of the potential for volatility, longer-term investors should tread carefully, and may want to take a more cautious tack.

“We’ve always taken a wait-and-see approach to that market,” Josef Schuster, founder of IPOX Schuster, an investment and research firm focused on IPOs, told CNBC Make It in April.

If you want to get in on SpaceX, or any IPO, you’d be wise to do some homework on how these stocks tend to behave, Schuster and other experts say. Here’s what they say you need to know.

If SpaceX ends up bringing more retail investors into the fold than usual, it might be for a couple of reasons, Ritter says. For one thing, he says, SpaceX’s sister company Tesla has a large share of its outstanding shares held by retail investors, and Musk may want to repeat that model with SpaceX.

For another, “an investor in a stock is more likely to purchase the company’s products, in this case subscribing to Starlink or using X,” Ritter says. “Thus, a large retail allocation can improve the company’s cash flows as a result of more users of the products.”

If you want to purchase offering-priced shares through your online brokerage, you’ll likely have to put in a request to buy shares, Ritter says. And given the buzz surrounding SpaceX, expect some competition, he adds.

“A client of Schwab or Fidelity who asks for 500 shares … will [likely] receive fewer shares than requested,” he says.

If you’re unable to get shares at the offering price, you’ll have to buy them once they’re publicly available. And once shares hit the market, there’s no telling how any given IPO stock will behave, Ritter says: “On average, the open-to-close return is about zero.”

If you’re interested in buying into an IPO stock, experts say there are a few factors worth considering. Here are three to watch for.

1. Float

The percentage of a firm’s stock made available to the public, known as the stock’s float, is a key factor to pay attention to. A very low float is “a big red flag” in terms of which companies have historically performed or underperformed, says Schuster.

Issuing a small number of shares can help a company’s stock pop in early trading, he says, but could lead to ongoing volatility and outsize risk in the case that a company has negative news, such as failing to generate projected earnings.

With SpaceX rumored to go to market with about 5% float, the stock could be in historically tricky territory, Schuster says. “Anything below 7%, you have to be really careful.”

2. Sales

Once a company makes public filings with the SEC, pay attention to the firm’s sales, Ritter says.

Companies that have gone public with at least $1 billion in sales over the previous 12 months, have, on average, kept up with the market in the three years following the offering, he says, “whereas smaller companies on average have underperformed.”

In other words, companies with proven sales track records are less likely to underperform than those with a spottier history.

Still, you’ll have to decide, based on the company’s fundamentals, whether it’s worth holding long-term, Ritter told CNBC Make It earlier this spring. While IPO companies have tended to underperform when their share price vastly outstrips sales, a stock still may be worth buying if you believe, for instance, that a firm will be able to rapidly and consistently boost its financial performance in the years to come, Ritter says.

3. Portfolio role

It’s important to examine the role you’re hoping a particular IPO stock could play in your portfolio, experts say. Schuster says he generally favors investing after a stock has had some time on the market and cautions against trying to play the big, short-term swings that can come in the immediate aftermath of a public offering.

“I think investors really need to be careful of jumping in at this point,” he says. “However, down the road, once it starts trading, I think, let it trade and see. The entry points to IPOs have been, in many cases, much lower than the first trading day. [Some companies] haven’t been winners when we bought them on the first day or at the first close, but they’ve become winners over time.”

Both Ritter and Schuster caution against betting a large chunk of your portfolio on any single IPO stock and recommend holding any investment as part of a larger, diversified portfolio. It’s also smart to speak with a financial advisor before making any changes to your own portfolio.

And if you want early access to SpaceX or other pre-IPO names, you may already be able to get them as part of a more diversified strategy.

Mutual funds are allowed to hold up to 15% of the portfolio in so-called non-liquid assets, which can include private equity and private real estate holdings. Baron Opportunity, a mutual fund seeking to invest in innovative, fast-growing businesses, holds 13.8% of the portfolio in SpaceX at last report.

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