When you did not own full amount to buy house then you should wait till you arrange the full amount or try your level best to borrow interest free money from someone. It is unlawful to take interest based loan without a severe need. However, if you have taken the interest based loan then you should pay it off as soon as possible and keep on doing taubah and istighfar as well as you should avoid it in future.
Allah knows Best!
Darul Uloom Deoband