(1) In this section -
"conversion expenditure" means, subject to subsection (2), expenditure incurred on -
(a) the conversion into a house of a building -
(i) the site of which is wholly within a designated area, or which fronts onto a designated street, and
(ii) which has not been previously in use as a dwelling,
(b) the conversion into two or more houses of a building -
(i) the site of which is wholly within a designated area, or which fronts onto a designated street, and
(ii) which, prior to the conversion, had not been in use as a dwelling or had been in use as a single dwelling,
and references in this section and section 47 to "conversion", "conversion into a house" and "expenditure incurred on conversion" shall be construed accordingly;
"qualifying lease", in relation to a house, means, subject to section 47(3), a lease of the house the consideration for the grant of which consists -
(a) solely of periodic payments all of which are, or fall to be treated as, amounts by w