Society president Kevin Dey said the decision to put the house, at 14 King St, up for sale or commercial lease was made at a special meeting on November 8 called to discuss the society's financial difficulties.
Mr Dey said the economic downturn had caused income from grants, donations and investments and proceeds from its annual street appeal, to all fall significantly, resulting in monthly deficits in the thousands of dollars.
The society had been left with no option but to try to make better economic use of its main asset.
"A budget by our treasurer showed that if we don't arrest the downward slide, we would be eating into reserves," Mr Dey said.
The society employs a full-time field officer who cares for 82 clients, while its other expenses include a vehicle, building utilities and a monthly newsletter.
The society bought the house in 1985 with money from a bequest.
Mr Dey said the society's preferred outcome was to lease the building and use the rental income to help fund the society's work.
If its financial situation improved, it could consider eventually returning to the building.
The alternative was to sell the building and invest the proceeds, he said.
Society treasurer Alistair Swann said the financial difficulties had only arisen in the past year; however, if the monthly deficits continued at their present levels, the society's reserves might last only another two years.
Mr Swann said September's annual street appeal had yielded only $1900 - 20 per cent down on last year's figure - while in the current financial year, beginning on April 1, the society had received only $2500 in grants and donations.
With less than half the financial year remaining, it was unlikely to receive half of the previous financial year's total of $10,900, he said.
With the society receiving only $9300 in annual funding from the Ministry of Health, Mr Swann said his projected budget through to next June indicated the society would face a total deficit of about $20,000, which it could cover only by spending cash reserves.
To compound the society's financial woes, 75 per cent of its mortgage investments had been frozen, meaning it was receiving no interest income from them and would have to wait up to two years get its capital returned.
Mr Dey said the economic downturn meant charitable organisations were competing for a smaller pool of money.
"Every incorporated society is facing similar problems - the normal donations just aren't coming in."
Fundraising was particularly difficult for multiple sclerosis (MS) because the disease was not widely understood by the public, he said.
Because MS affected every sufferer in a different way, it was difficult to characterise when marketing a fundraising campaign.
One society member has taken to fundraising to try to alleviate the society's financial woes.
Timaru woman Jo Tatnell, who was diagnosed with MS eight years ago but is now in remission from the disease, began selling raffle tickets this week for an outdoor table and chairs given to the society by Washdyke companies ANDAR Holdings and Placemakers Timaru.
She had been leaving books of the $2 tickets at Timaru companies and stores, and next week would sell them in the town centre.
Miss Tatnell said she knew the society faced an uphill battle to raise money, but had still been shocked by the decision to sell or lease its house.