The stock market is in sell-off mode at the moment, in an apparent continuation of what was a dismal year in 2022. Investors have been grappling with the effects of elevated inflation, which topped a 40-year high last June and sent interest rates climbing rapidly. 

Consumers have ultimately been left with a weaker financial position, which means less spending, and therefore less revenue for businesses. In that context, it's no surprise that the benchmark S&P 500 stock market index is down more than 20% from its all-time high. 

But a new headwind emerged last week with the collapse of SVB Financial, the owner of Silicon Valley Bank. It sent the financial sector into a tailspin, and investors are still assessing the damage.

Like most stock market declines throughout history, however, this one could be a great buying opportunity when looking back on it in the future. Not all stocks are the same, though. Here's why shares of Bill.com (BILL 1.69%) could be a buy, whereas shares of Robinhood Markets (HOOD 2.58%) might be worth selling. 

1. Bill.com faces an enormous financial opportunity

Running a small business isn't easy. Being a sole proprietor means wearing multiple hats; you have to be the operator, the financial controller, the bookkeeper, and even the technology officer. But innovative software platforms have made almost all of those jobs much easier than they used to be, and Bill.com is one of the contributors. 

It's focused on streamlining the accounts payable, accounts receivable, and expense management processes by shifting those workflows online to the cloud. Its flagship Bill.com platform serves as a digital inbox designed to host a business's incoming invoices, helping clean up the paper trail. Once an invoice is in the inbox, it can be paid with one click, and the transaction is logged with the operator's choice of bookkeeping software. 

As of the fiscal 2023 second quarter (ended Dec. 31, 2022), Bill.com served 435,800 business customers across its portfolio of products. That's a long way from what it estimates could be more than 70 million businesses in its addressable market around the world, so the company's runway for growth is substantial.

Moreover, most of Bill.com's revenue comes from transaction fees generated when customers make a payment through one of its platforms. It has processed $253 billion in volume over the past four quarters, but that's a drop in the bucket compared to what is now an estimated $125 trillion market opportunity.

The company has told investors to expect $1 billion in revenue during fiscal 2023, which would be a 57% increase year over year. That growth rate is slower than fiscal 2022, but the economy is weaker now, and Bill.com is sacrificing some growth to improve its bottom-line losses, which like many young company are the result of investing in growth.

Investors can buy Bill.com stock now at a 77% discount to its all-time high. With such a big potential growth runway ahead, it feels like the stock market sell-off has served up a great buying opportunity. 

2. Robinhood's business might struggle to recover

Robinhood stock is down 89% from its all-time high, and while that's somewhat worse than the plunge in Bill.com stock, there is a key difference: Robinhood's prospects for a sustained recovery are relatively bleak based on its dismal financial results over the past six quarters.

The company soared to prominence during 2020 and 2021 as the brokerage platform attracted younger investors, many of them new to buying equities, after big gains in the major U.S. stock market indexes. The Robinhood mobile app made investing easy with a clean user interface and zero commissions on trades. 

But that could turn out to be the company's greatest weakness. Instead of charging commissions, it generates revenue under a model called payment for order flow. This meant, in essence, that it was selling buy and sell orders to traders, who weren't motivated to get the best prices for investors. This practice is under ongoing scrutiny from regulators

Of more immediate concern is Robinhood's underwhelming financial results since the stock market of 2021 cooled off. For example, the number of monthly active users on its platform peaked at 21.3 million in Q2 2021, and it has declined every single quarter since, coming in at just 11.4 million to end 2022.

On top of that, customers are holding the lowest dollar-value of assets in their Robinhood accounts since the end of 2020. That figure was $62 billion in fourth-quarter 2022, down from a peak of $102 billion. That creates a challenge because the company relies on transaction value to generate revenue, so if its fee base continues to shrink, it has little hope of generating long-term revenue growth. 

Investors have made their position crystal clear. They value Robinhood at $8.1 billion right now, but since the company has $6.3 billion in cash and equivalents on its balance sheet, they're only attributing $1.8 billion in actual value to the business itself. That doesn't inspire much confidence in a recovery.