I received an invitation as well, though I did not pay attention to it, while there are alot of scams out there it's better to be safe rather than do work expecting that you have spent 2-3 hours on a paper only to get either rejected due to some lame excuse or they don't look at your review at all therefore wasting your time.
I think that you received this invitation from an unreliable source (can you reveal the link/mail adress?). I think the Well-Online company might be very well legit http://wellonline.uk They are linked to “WAGENINGEN ACADEMIC PUBLISHERS” https://www.wageningenacademic.com nowadays linked/owned by Brill Publishers https://brill.com/publisher/BWAP and this publisher is genuine and legit.
Again I think you receive this invitation not from them but from a dubious agency. Furthermore offering co-authorship sounds like a paper mill operation, see for example:
Article Publication and collaboration anomalies in academic papers o...
Article Retracted papers originating from paper mills: cross sectional study
The offer to pay you 30 USD per review is suspect since peer review is voluntary and (in most cases) an unpaid part of the kind of work a researcher/expert performs. If this would be part of the way this company operates this would be prominently mentioned somewhere on their website (at least I was unable to find anything close to this).
All and all I would say I would not trust this invitation and again I would be interested in the details that tells you something about who send this invitation.
I'm Nancy, a researcher at Well-online, the flagship editorial service of the UK's Well-online Science Press. In the in-depth study and extensive exchange of the latest academic achievements in the field of philosophy, we deeply admire your outstanding contributions and profound attains in this field. Given your position of authority and insight in this field, we invite you to join our team of reviewers to promote the further development and wider dissemination of philosophical research.
As our permanent reviewer, you will be responsible for evaluating papers submitted to Well-online in the field of philosophy, providing valuable input on multiple dimensions from academic originality to logical rigor. We believe that your professional perspective will greatly improve the quality of the manuscript and promote the healthy exchange and development of the academic community.
In recognition and respect for your hard work, we offer a payment of $30 per review, which will be settled through PayPal, a secure and convenient payment platform. Rest assured that we are committed to complying with international standards in all payment processes to ensure that your rights are properly protected.
Other cooperation opportunities:
In addition to its review work, Well-online is committed to providing a diverse range of paid academic collaboration services, including but not limited to:
Article writing: According to your research interests and expertise, we can arrange customized article writing projects.
Review of Published articles: Write in-depth reviews of published articles in the field of philosophy, as opposed to reviewing manuscripts, this will be a platform to showcase your unique insights.
Citation Collaboration: If your paper is under review, minor or major revisions are being made, and you plan to submit revisions later, please let me know.
If you are interested in this invitation, or want to know more about the cooperation details, please feel free to reply to this email. If you have any cooperation ideas related to the publication of this article, please do not hesitate to contact me. We look forward to establishing a long-term and fruitful cooperation relationship with you, and jointly contribute to the development of the field of philosophy.
"In addition, in order to enhance the dissemination of academic achievements, well-online has established long-term cooperative relations with world-renowned publishing houses such as Springer, Elsevier, IEEE, Wiley, Matec, Taylor, Francis, Hindawi, Francis Academic Press, WIT, and ASME dedicated to promoting the process of non-profit public welfare organizations with high-quality global academic standards. To find out more about our expert services visit www.wellonline.uk."
I have found that WAP no longer is independent it is now owned by Brill - so I wrote them (no answer so far). I wrote to Wellonline to ask what happens. They have sent me 6 different paper titles that need review. YET no process, and no journal name yet.
IMHO I think that they are a paper mill and accept anything, but it is too early to tell yet if they a. pay if you do review; b. publish with a proper peer review process and c. if these are going to be published in a proper journal.
Normal process is a named editorial board and that papers are rejected if unsuitable. Not mentioning a rejection rate makes me wary.