They are looking for a company or freelancer to write their RFPs. If you have never done that you don't have any idea how to formulate your proposal for the job.
An RFP is a request for proposal, in which one organization is asking others to submit bids for a project or a contract. For example a government agency writes an RFP to have technology companies design, build, and administer a cloud based system to allow in-field technicians to report their data and produce reports. AN RFP can be for as $10K project, or as large as multi-billion dollar project.
There is no way to say I will produce an RFP for $x without knowing many more details. This job advertisement is a RFP, and they are asking you the potential RFP writer to respond to that RFP with details on how you will do the job and what the costs will be.