Nervous landlords and buy-to-let investors who want to leave the market before further house price falls and realise their gains as quickly as possible will save thousands of pounds through a new online trading service launched today by iSTONE.

The system fundamentally challenges the assumption that residential investment property should only ever be bought and sold with vacant possession. Its web-based service, at www.istone.co.uk, allows property investors to trade tenanted property quickly, openly and profitably - without removing the tenant.

iSTONE is being launched at the Homebuyer Show 2005 today by Jonathan Warr, an experienced property investor and developer, who describes himself as "fed up to the back teeth with excessive agency fees and insistence on vacant possession, which puts landlords out of pocket, delays sales and deprives perfectly good tenants of a secure home."

"We call it Buy-With-Let," says Mr Warr, "iSTONE ensures investors keep receiving rental income until the sale is complete, and purchasers can gain the benefits of reliable tenants and guaranteed income from the start. It offers benefits to all types of investor, but especially those who need a lower risk, higher return route to market.

The savings are expected to be significant for vendors - estimated at £4,000 or more. As they are selling the property exactly as it is, they save the costs associated with serving tenants with a 'notice to quit', disposal of furnishings, the loss of rental income while the property is empty and being marketed, and estate agents' commission on the sale.

More bullish or long-term landlords who want to continue investing can search and buy suitable new properties with good yields and the tenants already in place. These purchasers are expected to save at least £2,500 on a typical deal, because they do not have to pay to find and contract a new set of tenants, they do not need to refurbish or refurnish the property to make it attractive to new tenants, and they achieve rental income from day one.

It's good news for tenants too, who otherwise risk the disruption, cost and inconvenience of losing their home and having to find somewhere else to rent when the landlord decides to sell the property - in many cases to another property investor who would be looking for similar sorts of tenants.