Making a condition that 30% of income from Masjid will go towards charitable works

"The individual intends to purchase land for a mosque, estimated to cost approximately £200,000, and intends to dedicate (waqf/وقف) this land for the mosque. However, there is a condition attached. After 4/5 years, once the mosque is established and funds start accruing through donations, etc., 30% of the money will be allocated to support the individual's madrassa for orphans in Afghanistan, following the clearance of all mosque-related expenses. In the event that the community does not agree to allocate this money to the orphan's madrassa, it can be directed to Afghanistan for various welfare projects, such as building schools, aiding the impoverished, reconstructing fallen bridges, or any other charitable endeavors." Please note that the renovation will take place through donation and not this particular individual will do all the renovation process all by himself. Is doing such thing ie; making such a condition that 30% would be spend there, is permissible according to Islam bearing in mind all the stated information. Please answer with evidences as answer will be shared with the community Insha'Allah later. Jazakumullahu Khair