From my personal opinion, if the 50% COV is enough to cover the 1 mth rental, I would not ask for the rental.
The seller may be really short of cash, that's why they agree to lower COV by 50%.
They will be grateful to you forever if you will help them tide thru and you really wouldn't loss out and have good blessing.
However, you have to make sure they are liable for all damages and utilities incurred during that period.