Here's a better scenario:
Create your MySQL database how you will and a table for the responses ('yes'). Relate this table to the task (or whatever) so you can reconcile tasks with acceptances.
Now you have three columns necessary:
client Reference Leading back to the client
Freelancer Reference leading back to freelancer
Client Accept a date/time field that allows NULL (initial value)
Freelance accept a date/time field that allows NULL (initial value)
Now you just stamp a field, if "yes" is clicked, with the datetime value of the moment it was accepted (extra data for free) instead of just a flag set to TRUE
Any with both fields with datetime are accepted and in addition a record now exists of when this was done. You can also work out an option for rejection by either if this is on a person-to-person solicitation basis. Or an expiration date.