How many residents are there total?
select count(*) from residents
How many different properties are there?
select count(distinct property_id) from properties
Show the property id and count of residents for the property with the most residents.
select t1.property_id, count(*) from properties as t1 join residents as t2 on t1.property_id = t2.property_id group by t1.property_id order by count(*) desc limit 1
Show this data for each property.
select t1.property_id, count(*) from properties as t1 join residents as t2 on t1.property_id = t2.property_id group by t1.property_id