The Grade II listed Northgate House in Sleaford is to become the new home of Wright Vigar chartered accountants.
Now the firm is hoping to spend up to £150,000 renovating the building before moving in next year.
Wright Vigar, which also has offices in Lincoln, Gainsborough, Retford and London, is based in Boston Road.
It plans to make Northgate House its Sleaford office and base ten members of staff there.
Partner James Sewell said the building would undergo a number of renovations, subject to planning permission.
“We are planning to remove an internal wall and create offices upstairs with a large meeting or function room downstairs,” he said.
“There is a single-storey prefab on the back, which we would like to replace with a permanent building.
“We are using a Sleaford architect. Part of the attraction was that they know the town and the significance of the building.
“The total investment in the renovations is likely to be between £80,000 and £150,000 and we hope to be in by May time.”
Mr Sewell said the company had outgrown its current offices.
“Wright Vigar has grown considerably over previous years. Four years ago we took over one practice in the town and last year we bought another in Dunston.
“Our offices in Boston Road have no frontage and people don’t know we are there. We are keen to keep growing and we think this will be a great move.”
For the past 60 years, Northgate House had been the head office of estate agents William H Brown. The firm has now moved to offices in Southgate.
Lincoln agents Hodgson Elkington LLP handled the sale on behalf of its former owners.
Sam Elkington said: “Initially, we were looking at either letting or selling it, but before we had the opportunity of putting it fully on the market we were able to put it to potentially interested parties.
“We felt, as this is a very prominent period building on one of the main arterial routes into Sleaford, it would make another excellent headquarters for a professional business.
“The building extends to a net internal floor area of almost 2,400sqft on two floors and has 16 car parking spaces on site.
“There is also a small retail kiosk included in the property, next to the main car park entrance.
“We approached Wright Vigar, which we knew was seeking a new prominent office in the town.
“We were able to offer this property on an ‘off-the-market’ deal and terms were quickly agreed for a sale.”