The once-clubby world of start-up deal making known as “angel investing” has had an influx of new participants. It’s part of a wider boom in ever-riskier investments.SAN FRANCISCO — On a recent Wednesday evening, 60 people gathered in a virtual conference room to discuss start-up investments. Among them were a professional poker player from Arizona, an allergist in California and a kombucha maker from Tennessee. All were members of Angel Squad, a six-month $2,500 program that aims to help people break into the clubby world of venture capital as individual investors, known as “angels.”The group listened as Eric Bahn, the instructor, rattled off anecdotes and advice from the front lines of start-up investing. “The most important question when you are an early stage investor is: What happens if things go right?” he said, stepping back from his desk and raising his hands for emphasis.Caroline Howard, 29, one of the founders of Walker Brothers Beverage, a kombucha company in Nashville, said the class taught her how to evaluate deals. “I think it’s so fun to see companies when they’re so young and have a germ of an idea and back them,” she said.Founded in January, Angel Squad is one of several ways that people from outside Silicon Valley’s investing elite are now joining the ranks of angel investors. The influx — which includes art curators, dentists, influencers and retirees — is transforming the way that start-ups raise money, upending the pecking order in venture capital and pushing a niche corner of the investing world toward mass adoption.“It is absolutely going mainstream,” said Kingsley Advani, founder of Allocations, a tech platform for angel investors. “It’s accelerating and it’s getting faster and faster.” He said even his mother, a retired schoolteacher in Australia, has invested in 41 start-ups over the last few years.More than 3,000 new angel investors are projected to make their first deal this year, up from 2,725 last year, according to the research firm PitchBook. And the amount of money that angels are pouring into start-ups has swelled, reaching $2.1 billion in the first six months of this year, compared with $2.6 billion for all of 2020, according to the National Venture Capital Association and PitchBook.Until recently, such investing was off-limits to most people. Securities rules restricted it to the wealthy because of the level of risk involved, since most start-ups fail. Even those who qualified often lacked the connections to find deals. And start-ups preferred to raise big slugs of cash from a handful of investors, rather than deal with the costs and headaches of processing dozens of tiny checks.But over the last year, many of those roadblocks have dissipated. Last year, the Securities and Exchange Commission loosened restrictions and began allowing people to become accredited investors — those allowed to back private start-ups — after passing a test. New tech tools are making the process of raising funds from many small investors cheaper and faster. And start-ups have become eager to add potentially helpful angels to their rosters of backers.The boom is part of a rush into ever-riskier forms of investment, driven by low interest rates, stimulus money and a little bit of “why not?” chutzpah. Nowhere is that sentiment stronger than in the tech industry, where start-ups are flush with cash, initial public stock offerings have been plentiful and Big Tech is delivering blockbuster profits.“Overnight, the entire world just woke up and went, ‘Oh, wow, we want to go invest in technology,’” said Avlok Kohli, chief executive of AngelList Venture, a company that provides tools for start-up fund-raising.Many new angel investors have some connection to the tech industry but are not the V.I.P.s who are normally invited into deals. Some are complete outsiders. Many are broadcasting their activity on social media and turning the investing into a branding opportunity, a hobby, a networking play, a social status or a way to give back.Karin Dillie, 33, an executive at an e-commerce company in New York, said she hadn’t realized that she could be an angel investor. But in June, when a business school classmate emailed asking her to help fund a calendar app called Arrange, Ms. Dillie decided to go for it. She invested $5,000.“I probably needed someone to give me permission to play the game because investing always seemed so elusive,” she said.Karin Dillie, 33, an executive at an e-commerce company in New York, said she hadn’t realized that she could be an angel investor.Elianel Clinton for The New York TimesMs. Dillie has since joined several informal investing groups, listened to podcasts and set up news alerts for terms like “preseed funding” (the earliest money a start-up usually raises from outside investors). She said she was motivated to support female founders, who raise less than 2 percent of all venture funding.In London, Ivy Mukherjee, 28, a product designer, and Shashwat Shukla, 30, a private equity investor, also started putting money into start-ups together this year to learn new skills and network with others in the industry. They said they were proceeding cautiously, with checks of $2,000 to $5,000, knowing they could lose it all.“If we happen to make our money back, that’s good enough for us,” Mr. Shukla said.The new angels have the potential to transform a venture capital industry that has been stubbornly clubby. They could also put pressure on bad actors in the industry who get away with things ranging from rudeness to sexual harassment, said Elizabeth Yin, a general partner at Hustle Fund, a venture capital firm. The firm also created Angel Squad and shares deals with its members.“More competition brings about better behavior,” Ms. Yin said. (In addition to investing in start-ups, Hustle Fund sells mugs that say “Be Nice, Make Billions.”)The angel boom has, in turn, created a miniboom of companies that aim to streamline the investing process. Allocations, the start-up run by Mr. Advani, offers group deal making. Assure, another start-up, helps with the administrative work. Others, including Party Round and Sign and Wire, help angels with money transfers or work with start-ups to raise money from large groups of investors.AngelList, which has enabled such deals for over a decade, has steadily expanded its menu of options, including rolling funds (for people to subscribe to an angel investor’s deals) and roll-up vehicles (for start-ups to consolidate lots of small checks). Mr. Kohli said his company runs a “fund factory” that compresses a month of legal paperwork and wire transfers into the push of a button.Still, getting access to the next hot tech start-up as a total outsider takes time.Ashley Flucas, 35, a real estate lawyer in Palm Beach County, Fla., began investing in start-ups three years ago. She said it was a chance to create generational wealth, something underrepresented people did not typically get access to.“It’s the same people doing deals with each other and sharing in the wealth, and I’m thinking, how do I break into that?” said Ms. Flucas, who is Black.But it took cold emails, research, building her reputation on AngelList and participating in three angel investing fellowships to get access to deals and construct a portfolio of more than 200 companies, she said. Things especially took off this spring after she invested in several companies that had just graduated from Y Combinator, the start-up accelerator. Some of her investments have appreciated enough on paper to return more than she has put in.Now, Ms. Flucas said, she is getting asked to join venture firms or raise her own fund. “The seeds I planted at the beginning of the journey are bearing fruit,” she said.“It’s the same people doing deals with each other and sharing in the wealth, and I’m thinking, how do I break into that?” Ms. Flucas said.Ysa Pérez for The New York TimesSome longtime angels have cautionary words for those just beginning their start-up investments. Aaron Houghton, 40, an entrepreneur, said he lost $50,000 that he had invested in a friend’s start-up in 2014, along with a $10,000 deal that went belly-up. He sarcastically called the losses a “really nice, somewhat inexpensive wake-up call” that showed he needed to spend more than a few hours researching companies before investing.But that isn’t always an option in today’s frenzied market. Mr. Houghton said he had recently been given little more than a pitch presentation, a high price tag and a few hours to decide whether he was in or out of an investment.“It’s all so hot right now,” he said.In the recent Angel Squad class, one participant asked if investors should be concerned about valuations. Mr. Bahn said it was up to each investor, but he added that there was an upside to the skyrocketing prices. Some tech companies were becoming huge, worth $10 billion or more on paper, creating bigger returns for investors who got in early. That was the exciting thing about investing in young start-ups, he said.“The alpha,” he said, referring to an investor’s ability to beat the broader market, “just continues to grow.” More