My best advise would be to fit a new battery, do all the tyre pressures and asses the tyre condition for perishing, try to free up the brakes so that it can at least be moved around and or loaded onto a trailer. Spend a solid couple of days giving it a really good clean up inside and out / polish so that potential buyers can actually see what they are buying. So many people will see that and walk away, not being able to see through the green mould. Even though it has its faults, make an effort to present the car in the best possible way you can. You will get back in money what you put in with time to properly present the car. Just my thoughts