The Encore Boston Harbor casino. State House News Service photo | File

Wynn Resorts will sell its Everett resort casino to a San Diego real estate investment trust and use the windfall to pay for new developments and retire debt.

The developer and operator of the Encore Boston Harbor casino said it will lease back the casino and 671-room hotel from Realty Income Inc. for annual rent of $100 million. The agreement also gives Realty Income an option to buy a 13-acre assemblage on the east side of Broadway, where Wynn Resorts is proposing a large entertainment complex.

Wynn said the sale-leaseback will be completed in the fourth quarter. It will continue to operate the property, which opened in 2019 and includes 3.1 million square feet of gaming and entertainment space and a 671-room hotel.

MGM Resorts International also sold and leased back its Springfield casino real estate, along with several other gaming facilities in its portfolio, to an investor-controlled shell company last year as a way to raise more capital.

In announcing the investment, its first in the gaming sector, Realty Income said the Encore property has potential to expand the $2.6 billion gaming market in Greater Boston which includes 5.6 million potential customers who live within a 90-minute drive  “by appealing to underserved premium regional customers.”

At the same time, Wynn is giving Realty Income a 6-year option to buy the 13-acre Broadway site in exchange for paying up to $20 million in additional rent.

Wynn Resorts has assembled 13 acres of developable land across Broadway from the casino site and released plans in December for an 1,800-seat theater and restaurant complex. This month, the company notified the Massachusetts Gaming Commission it would reduce the capacity of the theater to under 1,000 patrons.

The proposal generated questions about whether the project is subject to regulation by the commission, since it is located outside of the main casino property.

In an earnings report issued Tuesday, Wynn Resorts said the Encore Boston Harbor property recorded $15.6 million in operating income during the fourth quarter of 2021, rebounding from a $35 million loss during the same period in 2021.