That "small leak" is causing intense structural damage, which costs tens of thousands of dollars to repair, along with the deteriorating other areas, this means the house has horrible water leakage issues. The roof and the walls should not be "soft". Water damage is incredibly expensive to repair. I had a cinderblock chimney that had water leaking behind it that soaked the house frame down to the sill plate. It cost me over $20K to fix it and that was a deal from my son, who is a contractor.
So, unless you have the ability to borrow and pay back tens of thousands of dollars, your idea of selling out right now may be the wisest idea. No point in spending, say $75K on a house to "save" it to sell because you will not get one penny back from the sale. You see, people EXPECT to buy a house that is not falling down from rotting, regardless what you paid to repair water damage. The roof and leaks should have been fixed when water damage was initially present to mitigate further damages.
Remember, there is a huge different in REPAIR costs than HOME IMPROVEMENT costs in conjunction as to what is actually an investment. Yes, you can recoup a percentage of home improvement costs, but a solid roof and walls is something that is expected in a structure, so it is not "added value". Added value that can be recouped in a sale is renovating bathrooms and the kitchen, putting down new floors and updating light fixtures and appliances. That is where you can get a better price for a house. But, to boast that you paid, say, $75K on water damage repairs does not bring up the value of the house. That is like saying you want more money for a car because it has a new heater. Heat is expected in a car.
You may as well sell the house as is and have the buyer do the repairs because if you do the repairs, it will not put any more money in your pocket. The house will be sold for it's value, whether the roof leaks or not, whether the window sills and exterior siding are rotting or not. It will sell with or without the repairs, but you will not receive any payback for the repairs, so why bother??
If I were you, I would sell it because it is too big and too much money for your mom to live in such a large house to begin with. Set her up in a ground floor condo or a small ranch home, if possible.