Thank you for your question
My name is Clare
I shall do my best to help you but I need some further information first
On what basis are they currently living there?
When they purchased the house together was a Declaration of Trust signed dealing with how the equity would be shared between them?
How much is outstanding on the mortgage ?
So the property is worth £350,000 and there is £100,000 outstanding on the mortgage leaving an equity (allowing for notional sale costs) of £245,000
If there was no Declaration of Trust then your husband and his sister share that sum equally between them - so his offer to settle for £230,000 (to include the money to pay off the mortgage) is a fair one.
If he wishes to force a sale them he will need to write a formal letter to her saying that she either agrees to buy him out or to sell the property and if he does not have her proposals
within 14 days he will issue a court application
At the end of that time he can apply to the court for an Order for sale
He can read about the process here
Please ask if you need further details
Sorry - I thought you said that they purchased the property together?
But the property was placed in his sole name?