The £20m-turnover firm, part of construction group Willmott Dixon, is aiming at projects worth between £1m and £10m.
After Inspace has footed the bill for the work, clients will repay the debt at a fixed interest rate, typically over five years.
The firm aims to pilot the service over the next six months with two or three clients on projects valued at between £3m and £5m.
Inspace has linked up with a City-based leasing advisory service, which it declined to name, to underpin the service.
Managing director John O'Neill said the service had been conceived because many clients wanted to divest themselves of properties. He added that the scheme could proceed immediately. "We can press the button on this immediately. We have a number of funding institutions backing us."
Inspace has spent six months researching the service, and has held discussions with potential clients. O'Neill said some had shown a great deal of interest in the the package.
Inspace will consider widening the service to include higher value work if the trial is successful.
These may start with typical office fit-out projects, including those where Inspace had control over design.
Inspace was formed two years ago, and claims in its publicity material that it is one of the top five players in the London fit-out market.
O'Neill said the firm has concentrated on big-name repeat clients and has completed six projects for developer Marylebone Warwick Balfour and four for Nikko Bank.
Other clients have included Hilton Hotels, BT, Fortnum & Mason, BP Amoco and the Ministry of Defence.
The firm has created a network of interior specialists such as IT installers and architects that it relies on for specialist service.
As a group, Willmott Dixon's turnover increased 2% to £275m for the year to 31 December 2000. Pre-tax profits rose 25% to £3.8m.
