I have seen many job posts that indicate that the client will be hiring more than one freelancer. To facilitate the process, I believe that you would simply leave the job open after making a hire so that others could still apply. You may wish to indicate in your job posting that you will be hiring more than one person. Otherwise, freelancers may not apply once they see that someone has been hired.
Ana, there should be a place where you can indicate how many freelancers you need in your RFP. This means all bidders know in advance how many people will be involved and should not impact their willingness to bid.
re: "As a client, can I hire two or more freelancers to do the job?"
I usually hire multiple people to do a job.
That gives me more options.
And I can compare their work, and continue working only with the best.