Thank you for your question
You do not have to pay Occupational Rent on a monthly basis - it is simply a figure that is taken into account when the final distribution is made.
You will have to be given credit for paying the Insurance and the water rates and keeping the property in good repair
He cannot simply insist on selling at a lower price provided you are following the advice of the Estate Agent
If the solicitor has the statements your brother can insist on seeing them - so if you feel strongly do not give them to the solicitor.
You can offer him the choice - if he wants occupational rent then you want exclusive occupation so he does not get a key
You are most welcome