A sprawling Scottish castle is on sale for offers over £30,000 ($37,000), but there is a catch; its current owners estimate that it requires an additional £12 million ($14.8 million) for restoration.

Situated on Fetlar, the fourth largest of the Shetland Islands, Brough Lodge is in one of the most remote parts of the UK.

It's accessible via ferry from the Shetland mainland, which itself is an hour and a half flight from Edinburgh or a three-and-a-half-hour flight from London.

The island is home to around 69 people, according to the Fetlar Community Association website -- an increase from its lowest population of 48 in early 2009.

Nestled into the hillside, the castle overlooks Fetlar's grassland and rugged cliffs stretching down to the sea, as well as the surrounding islands.

Brough Lodge was built in 1825 by local merchant Arthur Nicolson in a Gothic style, said to be influenced by his European tours.

It has been empty since the 1970s, although it was made wind and watertight about 10 years ago by its current owners, the Brough Lodge Trust, following a fundraising campaign.

As well as the house, there is a courtyard, several walled gardens and an oval shaped tower folly, once used as an observatory and built on the site of a broch -- a type of Iron Age roundhouse unique to Scotland.

'World-class retreat' ambition

The Brough Lodge Trust is looking for "a philanthropic entrepreneur" who can transform the castle into a 24-bedroom retreat, and has already received several expressions of interest, it said in a statement to CNN Wednesday.

"Several potential investors have been in touch with our selling agents, some of them travelling to Fetlar to view the Lodge and talk over the possibilities with trustees," trust director Drew Ratter said in the statement.

"One potential buyer has put forward a detailed proposal and we are exploring it with them, but we would nevertheless still be interested to hear from other philanthropic entrepreneurs, as we would wish to achieve the best possible outcome for both the building and the community in Fetlar."

The trust hopes that the retreat will attract guests who wish to partake in various cultural activities, including textile making, which Shetland is famed for, yoga and guided wildlife tours.

"The vision is simple but effective: Brough Lodge, a category A-Listed Building set in approximately 40 acres of land, will be transformed into a world-class retreat that will delight all who visit it," the trust said on its website.

"Under the plans we have developed, the building's historic character would be fully respected. New accommodation, sensitive to its setting, would offer up to 24 double bedrooms and other essential facilities, including an elevated dining room."

The hope is it will also provide up to 14 jobs for the island community, where there are traditionally few employment opportunities.

The trust said proceeds from the sale will support its work preserving Shetland's tradition of hand-knitting by providing tuition for local school children.