Answer:
They are acquiring a principal dwelling and they have no current interest in the dwelling, so it is a RMT. Renting and living there does not represent a legal interest in the property.
Official Interpretation
2(a)(24) Residential Mortgage Transaction
5. Acquisition. i. A residential mortgage transaction finances the acquisition of a consumer's principal dwelling. The term does not include a transaction involving a consumer's principal dwelling if the consumer had previously purchased and acquired some interest to the dwelling, even though the consumer had not acquired full legal title.