R’ Meir says you cannot sell a shul even though it will be still used as a shul except if there is a condition that if they want it back they can take it. The Chachamim say you can sell a shul to even a private person as long as it is not used for a bath house, tannery, Mikva or a washing clothes water hole. R’ Yehuda says you can sell shul for a courtyard and the buyer can do whatever he wants with it.

Megila 3:3

R’ Yehuda says a shul even though it was destroyed, you cannot say a eulogy, twist ropes, spread out traps, spread out fruits to dry on its roof or use it as a shortcut.

If in the ruins grass grew, you shouldn’t detach it to cause grief so that eventually they will fix the shul.