1. At the outset, you need to realise that this is illegal and unlawful conduct on the part of the trustee in bankruptcy. A trustee in bankruptcy is a trustee as the name suggests. This means that the trustee must at all times act in the best interests of the bankrupt's estate and seek to get the best possible price for any sales or realisations of the bankrupt's assets. Here, the trustee is effectively seeking to increase the liabilities of your son by selling the property at an undervalue. This is in direct contravention of his duties as trustee. Additionally, the trustee is seeking to contravene provisions relating to money laundering by selling the property for cash. Accordingly, your son should report him to the court for his unlawful behaviour. Additionally, it is not correct for the trustee to seek to "muscle" your daughter by threats to her. The trustee is not correct in stating that your daughter will automatically loose should the matter go to court. Given the circumstances,s he will not loose at all but the trustee will, given his behaviour.
2. Your daughter should consider purchasing the house herself with the aid of some finance if this is possible. Additionally, any mortgage penalty incurred will come equally out of both your son's share and your daughters. It is again not correct to say that your daughter will bear sole liability for this cost. YOur son should consider getting the trustee removed on the basis of his bad conduct and unlawful behaviour. In this way he can ensure that a full price is achieved for his (half) share in the property. A new trustee will get a proper price. So I would suggest your son seek to get the matter before the court and remove the trustee in bankruptcy.
Thankyou. I will relate this information to them and I think it is time to challenge them.