All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
Some points of the question are rather general; we shall answer your question according to our understanding in the following points:
Firstly, it is impermissible for you and your husband to ask his mother to take a big (usurious) loan so that she can buy a bigger house in order to rent out part of it, even if she was already planning to take a loan anyway. Your request for her to take a bigger loan is impermissible because it constitutes asking her to commit a prohibited act and endorsing it.
Secondly, if the mother took the loan and bought a house or a plot of land, then it is not prohibited for you to rent it from her or accept it or part of it as a gift from her if she gifted it to you, because the prohibition of taking a usurious loan is related to the person’s liability, not to what is bought by the loan. This ruling also applies to what other people buy with the money of a usurious loan; engaging in financial transactions with such people over what they bought is not prohibited. For more benefit, please refer to fataawa 93774 and 102369.
Thirdly, the reason that you believe that this house or property will eventually be yours is unclear; it cannot be declared true or false because judgment on any matter is based on conceptualizing it. However, if you mean that the house would be eventually inherited by your husband, then only Allaah knows that; please refer to fatwa 238165 about the inheritance between Muslims and non-Muslims.
Allaah knows best.