We use RTKLIB for that. It is free and open source. Emlid has their own flavour, which is downloadable right from the page as you read the official POST-PROCESSING GUIDE in the docs.
While it may be true for the software version you are currently running, that is not a correct statement. CSV export has been available as one of the export options in the ReachView DEV (development) version since this public news announcement on Dec 18, 2017. You could have switched to DEV version at any time since then by clicking that button in ReachView. But even better than that, you could have easily upgraded your ReachView stable version to get CSV export according to this recent public news announcement from 3 days ago.
Now, I’d also like to clear up a misconception you may have based on the way I read your post:
- The survey tool export files are final products. They do not get post-processed, and they will not convert to RINEX OBS files.
- The raw data log that you choose to record (in the logging tab) is automatically converted to RINEX when logging is finished. The appropriate RINEX files are included in the compressed ZIP file that you will download.
To give some background information, the survey tool is currently designed for RTK use and so it can’t be expected to automagically work for PPK without traveling forward in time to retrieve the accurate solution data that you will be doing the post-processing for later. I don’t mean that in a cheeky way, but just to make the point that when you are set up for PPK work, your rover when collecting points is doing so in single mode which is neither RTK or PPK and by that nature the points collected are not what we consider accurate. The accurate solution data will be determined later by a different piece of software called RTKPOST (see the docs).
The solution to the time-travel catch-22 situation is that while in single mode and your rover is logging raw data for PPK, you set up a survey project to collect single mode points. Later, when post-processing your raw logs, you can download the CSV survey project; grab the columns with point name and start/end times and discard those inaccurate coordinates. Now, with a table of the start and end times for each point, you can then retrieve the accurate position data from your processed solution file based on those times. There are ways you could automate the process, but it is worth noting that the program RTKPLOT (see the docs) has a manual process to view data from any of your collected points, based on their start/stop times, along with statistical information which may be helpful as well.
I hope that helps alleviate your fear of wasting your money. Surely, you must have known that people have been doing PPK with Reach and Reach RS from the beginning! 
One more thing. If you don’t like this PPK workflow, there are other ways to approach it, plus I believe there is non-free software available that can automatically do some of the work for you.