By Tony Booth

One of the consequences of the buy-to-let success story has been a huge increase in the volume and variation of loan products entering the market.

In recent months, lenders have relaxed their rent to loan criteria ... and this may be seen as good news for some, but a temptation too far for novice investor landlords.

When buy-to-let mortgages first entered the market - and for many years afterwards - they restricted lending by linking the monthly rental income to 130 per cent of the maximum monthly mortgage payment.

This was mainly a reflection of the level of apprehension lenders had at the time, offering risky new products in an undeveloped market.