Long before Illinois' same-sex marriage law was even up for a vote, the Rev. Pam Magnuson felt it was her calling to help the couples exchange vows and proclaim their lifelong devotion to each other.

But once gay marriage becomes legal across the state Sunday, Magnuson, who is a Universal Life minister and wedding officiant, expects to be busier than ever.

Not only will the law allow thousands more couples to obtain marriage licenses, its official implementation comes just as the busy summer and fall wedding season begins.

"I've already seen an increase in business and interest," said Magnuson, who owns the Pine Manor wedding venue in Mount Prospect. "This is an exciting time because we are demonstrating that all humans deserve the same rights."

Other marriage-related vendors say that as the new law's effective date approaches, they're also seeing a swell of same-sex marriage business.

At Amy Beck Cake Design in West Town, they're working on more cakes for same-sex weddings later this year, the owner said. Tasty Catering in Elk Grove Village has tripled its same-sex wedding business for June of this year compared with last year, officials there said.

While same-sex couples in some parts of the state have already been legally married here — Cook County, for example, is one of 16 counties that began issuing same-sex marriage licenses early — other counties decided to wait until the law officially goes into effect before issuing same-sex licenses. In addition, thousands of couples who already have civil unions will become eligible to transfer those documents into a license.

Many of those couples will want to mark the occasion with a special ceremony and put officiants, caterers, planners, florists, pastry chefs, clothing designers and vendors that cater to events to work, observers said.

"People were living without the legality. So now we're seeing a spike in (wedding) business, but it's not what people expected," said Marie Hale Ramos, the assistant director of the Chicago Area Gay and Lesbian Chamber of Commerce. "It's not a rush to the altar, but an array of different wedding styles and ceremonies."

The new law has encouraged a growing number of business owners and vendors to come forward to publicly support the gay and lesbian community, Ramos said. Courting new same-sex clients may translate into a sort of activism as more businesses embrace same-sex couples and nontraditional families, prompting others to follow.

Illinois could also attract same-sex marriage seekers from other states where their marriages aren't legal.

"When other states started removing their bans on gay marriages, we saw our couples going to other states to marry," Ramos said. "Now we can capture that money locally. And we can be supportive of our community in neighboring states that don't have supportive laws. That will result in a flush of cash and a flush of new residents who prefer to live where the laws support them."

According to the Williams Institute, a national think tank based at the University of California at Los Angeles, extending the right to marry to same-sex couples should generate up to $103 million in spending in the first three years of the law.

A study conducted by the group predicts that Illinois' wedding business will see an increase by $74 million by 2017, and the state could see an increase of $29 million in tourism expenditures made by out-of-town guests by then.

The boost in wedding spending would generate about 281 jobs in the state, the study found.

Businesses are banking that same-sex wedding couples may even spend more on their weddings than heterosexual couples. Studies have found that gay couples have higher household income than heterosexual couples and that LGBT consumers are better at managing their money.

Experts have also said that states that ban gay marriage, like Indiana and Wisconsin, lose a diverse workforce and sometimes lose business as same-sex couples chose to live, spend and host their events in more friendly regions.

Mignonette Bridal in Lakeview has seen a jump in lesbian weddings over the past three years, said the owner, Kpoene' Kofi-Nicklin. She's currently dressing five brides for same-sex weddings, an increase from last year, she said.

"The marriage (law) is making people excited," she said. "They're ready to get married. They're ready to go shopping."

At Robert Allerton Park in Monticello in central Illinois, same-sex couples could always rent the mansion and idyllic garden venue to host their receptions and ceremonies. Still, inquiries are up, said Jordan Gifford, the venue's wedding coordinator. The venue is making minor adjustments to accommodate their growing client base.

"We're looking at rewording our current documents that currently say 'bride and groom' to be more inclusive so the language will cater to everyone, including same-sex couples," Gifford said. "Outside of that, we will treat their bookings like we treat all others. All our staff are comfortable with gay marriage, and we welcome everyone."

To celebrate the new law, Chicago's Museum of Contemporary Art and partners have planned complimentary wedding ceremonies for several same-sex couples, which will take place Monday. That's generated even more interest for bookings, said Gina Crowley, the director of special events and rentals.

The Chicago History Museum recently hosted its first gay-targeted wedding expo, bringing together upscale vendors eager to work with same-sex couples while also showing off the museum's space as a potential same-sex wedding venue.

"The same-sex community is a new opportunity for growth," said Barbara Siska, director of corporate events. "We wanted to let them know we are one of the top wedding venues."

Getting married is not just about a party, said Leon Finkel, managing partner with Berger Schatz, a matrimony and family law practice in Chicago that says it has taken a special interest in serving same-sex couples. It's also about merging assets, building a family and creating a legacy, he said.

"Getting a marriage license is not something one should do without considering the obligations that go with it," he said. "Because this is the first time this community can marry, you will see a large population of older couples getting married for the first time. They have already established wealth, some may have children and there is a lot to consider in these situations."