Freelancing-marketplace operator Fiverr International (FVRR -3.33%) is one of my best investment ideas these days. The stock is deceptively cheap right now, and I think we're watching the early days of a future giant.

Here are three reasons why I bought some Fiverr shares a few months ago, and why I'm thinking about adding to my investment in this exciting growth stock.

A world globe surrounded by large piles of golden coins.

Image source: Getty Images.

1. Addressing a massive global market

In regulatory filings related to the initial public offering (IPO) two years ago, Fiverr said that the domestic market opportunity is worth about $100 billion in annual sales. The addressable market is many times larger on a global level. Furthermore, Fiverr's estimate comes from a time before the coronavirus pandemic accelerated the freelancer market in a big way.

It's true that Fiverr isn't the only game in town. The company faces serious competition from arch-rival Upwork and several smaller companies. However, Fiverr offers a unique combination of lightning-quick sales growth and sector-leading gross margins. Taken together, these qualities show that Fiverr is an established leader in its chosen field.

And there is plenty of room for several winners in the thriving market for freelance services. Fiverr collected $252 million in revenues over the last four quarters. Any way you slice it, that's a rounding error next to the enormous bulk of the total freelancer sector -- domestic and/or global. This company has only just begun to scratch the surface of a truly gigantic target opportunity.

2. Spending money now to make money later

Fiverr is not satisfied resting on its growing pile of laurels but is investing heavily in the technologies and services that will continue to deliver business growth for the long haul. It spent 30% of its gross profits on research and development over the last year. If you build a great service, the customers will come. Sales and marketing accounted for a 64% slice of the same gross-profits pie. Spreading the word about Fiverr's freelance-services platform is a necessary piece of the growth puzzle.

These ratios remind me of the pedal-to-the-metal model Netflix employed in the early days of its video-streaming business. Fiverr picked a fantastic role model. Netflix pumped 19% of its 2019 gross profits into research and development expenses and another 40% into sales and marketing. That blitz paid off in spades as Netflix's market cap rose from $2.9 billion to $242 billion in the 12 years hence.

I can't guarantee that Fiverr will follow a similar skyrocketing trajectory over the next decade -- but it wouldn't surprise me, either. The company is setting itself up for a long future of powerful growth based on the one-two punch of strong innovation and generous marketing programs.

Green sprouts growing on top of coin stacks of increasing height.

Image source: Getty Images.

3. No, Fiverr won't fade when we beat COVID-19

Many Fiverr investors seem to be convinced that the company's fortunes are tightly connected to the coronavirus pandemic. As a result, the stock tends to jump when the virus develops another dangerous mutation and fall when vaccines reduce infection rates. I don't see it that way at all.

Yes, Fiverr got a boost from the pandemic. But the lift should have long-lasting effects, leaving Fiverr with benefits far beyond the end of the pandemic itself.

Freelancers searching for gig opportunities who had never heard of Fiverr before will not forget about this impressive platform. The same goes for the people and companies that needed freelancer assistance during the health crisis. And I already mentioned how Fiverr is reinvesting the windfall from its recent business growth into more revenue-generating opportunities. That's another effect that won't be undone when we finally beat the virus.

Fiverr shares are trading nearly 50% below the all-time highs of last February, all because people have started to see an end to the pandemic and concluded that this would be bad news for Fiverr. Well, that's a wide-open buying window if you expect Fiverr's sales and profits to remain strong for years to come.

You get what you pay for in the long run. Fiverr deserves a premium valuation, thanks to large reserves of high-octane growth fuel and a massive target market. If nothing else, you should keep an eye on this stock and buy it on the dips.