If you are getting a mortgage, you usually buy it.
Also, if you want to get a mortgage for a lease, you can, if the mortgage repayment deadline is before the lease expiry. When it comes to property banks only care about getting a notarized mortgage contract and getting on the property's land registry sheet in a first position. (And this latter part is interesting, because most land registries - as far as I know - don't really have the concept of expiring records - so you can't record the fact of your lease.)
Also, if you want to get a mortgage for a lease, you can, if the mortgage repayment deadline is before the lease expiry. When it comes to property banks only care about getting a notarized mortgage contract and getting on the property's land registry sheet in a first position. (And this latter part is interesting, because most land registries - as far as I know - don't really have the concept of expiring records - so you can't record the fact of your lease.)