It should be from someone who uses that person.

Of course most GPs have personally put in money to keep the deals from sinking.

Or a personal loan if interest rates aren't cost prohibitive?

Buy it personally, and rent it full time to my C-corp?

I don't know if they still do it but if memory serves a few years ago TD Bank would do a HELOC on a rental in second position but only if it was titled in someone's personal name. 

While this job could be performed remotely, working with my peers in person for at least a year is important to me.

When your LLC takes a loan, expect as members to personally guarantee the debt.

My recommendation would be to engage an investment property focused realtor (not a general residential realtor) and let that person guide you through the process from pre-qualification to market/property valuation and selection. 

Unfortunately, this problem waste a lot of my time that could be spent on other investments.I have used the same tax professional for many years and he is very educated, but also much older than me and it's hard for me to understand all the reasons he has expressed why is better to put the rental on my personal tax returns.

So the question becomes based on their individual and personal tax situation what is the estimated tax burden they'd save?