I am an independent researcher and have spent the past year writing a fairly extensive (60+ pages) research paper on a topic in probability/statistics. The paper is almost complete but there are a couple minor loose ends that I am having issues with proving. Furthermore, given the length of the paper I am not sure of the appropriate journal to submit for publication and thus am considering contacting relevant professors in academia for help/guidance. My plan was to offer co-authorship in exchange for help addressing these loose ends and guidance with the publication process. That said, my impression is that research faculty are inundated with these sorts of requests and so I was not sure if this approach was likely to get a response. Is this practice frowned upon in academia? If not, are there general best practices for reaching out with these sorts of requests?