OS we hid it from our new landlord until we were in for a few months, as we really needed somewhere new at short notice and was worried they wouldn't take us in. When we did tell him he was absolutely wonderful about the whole situation!!
It can definitely affect loan applications as they ask for current salary details to ensure you can meet repayments, however you could technically get away with it by not declaring your pregnancy. You generally can't once your pregnant if only receiving smp and not entering into it with your partner/husband!!