I'm sorry you are in this difficult situation . I understand that you want to support your brother, whatever his problems are ( I've not read your other threads ) .
TBH the house sounds like it's in a bad way and will need at least 10k ( very rough guess ) to make it habitable, assuming that's it's structurally sound and roof, heating and plumbing are ok. That's just kitchen, bathroom , basic decor , floor coverings .
If it needs rewired, replumbed, new boiler , repairs to roof or windows, replastering - you are looking at more. Lots more .
If it was that easy to buy a house in poor condition and do it up easily and cheaply , everyone would be doing it . I'm sorry, but that's the reality. It takes time, money and hard work and it's a lot of hassle . Especially if you want to project manage it or live in it while the work is going on .
Do you have that kind of money ?
If you don't have the skills to manage such a project, can you get them ?
Can your brother live there while this is going on ?
Once it's in good condition, will your brother be able to maintain it in a reasonable state ?
Of the answer isn't an enthusiastic " yes" , You might be better to think of selling it , as a PP suggested, and buying a small easily managed modern flat. Or to think of some other options .