"rent it out"
Your mum seems to have no idea about the realities and responsibilities of being a landlord. You really don't want the hassle for a house you'll never see the benefits of, and your brother seems to be someone who would be ill equipped, to be landlords. Tenants can be an absolute nightmare and you can end up in a whole heap of trouble if you haven't done things 100% correctly. If it has to be rented, I'd honestly look into giving your half of the house to your brother and walking away from the whole shit show.
Since you're doing all the work, and paying for the solicitor I presume, don't get sucked into paying for advice for your brother (who appears not to GAF about you and is treating you like staff) and focus only on sorting out what's in your best interests.
From what you've written this seems to be a family dynamic of the narcissist parent, golden child and scapegoat. Just because you've been trained since birth to run round doing what's best for everyone else and ignoring your own needs, that doesn't mean life is meant to be that way or that you have to continue doing it.
Do what's best for you here, ensure you're not caught up in any sticky situations and leave your brother to get on with it. You're not his keeper, you don't have any responsibility for him, if he ruins his life and squanders his inheritance that's not your problem. Just make sure there's no way he can take you down with him.
And if I'm right about the family dynamics then don't put yourself in a position where you can't walk away from any relationship with him if you choose to do so. If you stop acting like his personal staff, he may turn on you and you may decide you want nothing more to do with him. So think carefully about being tied to him with a jointly owned property.