Query returns 'Empty set' in MySQL

Can some one help me to spot where I am missing something. Following query returns empty set:

SELECT membership_price_monthly / lifeguard_salary_hourly AS hours_needed
FROM membership m
JOIN household_member h ON m.household_member_id = h.household_member_id 
JOIN lifeguard l m.pool_id = l.pool_id 
WHERE lifeguard_id = '9775463'
  AND m.household_member_id IN (
    SELECT household_member_id 
    FROM household_member
    WHERE household_member_lname LIKE 'M%'
  )

The four tables are: