My current lender is confusing me
In a phone call this morning she said I would want a residential mortgage and then she went to talk to a colleague
She then called me back and said they could only offer me a buy to let but they wouldn't take rental income into account - so she had me agree that I would have a buy to let and not knock through until I'd paid off the mortgage
Does anyone know why they won't take rental income into consideration 
I have a mortgage with them. I wanted to buy next door and knock through and have one place.