leasing a property for free but wish to take back

My mother a retired public school teacher entered into a 10 yr contract with the barangay day care. They are allowed to put up a small concrete school building in a vacant lot infront of our house for free, meaning they(the teacher in charge) will not be paying my mother not even a centavo for the ten years of using our property but will turn over the ownership of the school building to her. But lo and behold now nearing halfway(5 yrs) the teacher incharge came to my mother with a new set of contract with an insertion of a statement that my mother need to pay them " some money" at the end of ten years since the teacher in charge said that she put up personal money in the school building...and so in verbal my mother agreed to pay them 50K at the end of the 10 yr contract but will get the money from the school nursery students collection of 500 pesos per month...but the teacher in-charge is so deliquent in giving her the agreed 500 pesos...so our family is contemplating of getting day-care school out of our property by reason that aside from using our property for free, we are even the one cleaning our front yard since the everyday the students and their mothers leave garbage all over, mothers behavior are unruly,and so noisy...so please can anybody with a good heart advice US on what we can do or what legal things we can cling into..so that we can get them out of our property...thanks very much