What is the ruling on living in residential compounds where residents pay a monthly fee for services (such as water, gas, security, and waste disposal), with varying usage of water and gas among them? Is this considered a gharar (uncertainty) sale? And is it permissible to own a house in these compounds?

If the owners agree to pay a fixed monthly amount to cover the costs of services (water, gas, and security) and overlook differences in consumption, there is no harm in that. Any amount exceeding an individual's consumption would be considered a donation from them. The gift of an unknown amount is permissible according to the most authoritative opinion among the Malikis and others. Something similar to this has been mentioned in the Sunnah, known as "al-nahd" or "al-tanahud," where each companion contributes a portion of the expenses so that they can all eat together, and there is no harm if some eat more or give some away in charity.