All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
You are not permitted to purchase a house through usury-taking bank since the situation you mentioned is not a dire necessity for which committing what is forbidden could be permitted.
As you know, the dire necessity for dealing with usury is only when one does not have anything to feed himself and if he does not consume what is forbidden, he may face death or one does not have any cloth to cover himself other than using Riba or he could not find any accommodation to live in. In these critical and dangerous situations one may deal with Riba, otherwise it is not permissible to commit what is what is forbidden in the Sharee’ah.
Allah Says (what means): {…while He has explained to you in detail what is forbidden to you, except under compulsion of necessity? …} [Quran 6:119]
Allah also Says (what means): {… But whoever is forced [by necessity], neither desiring [it] nor transgressing [its limit], there is no sin upon him. Indeed, Allah is Forgiving and Merciful. …} [Quran 2:173]
The Muslim scholars define the necessity that one is in a so serious condition that if he does not consume what is forbidden he may die, or he may face an unbearable hardship or he could not even live as a poor person lives.
When the necessity comes to an end, one has to immediately stop using what is forbidden or dealing in it.
Allah knows best.