@Devin PetersonAs someone who does some private lending I have an attorney create the documents and closing package which we pass on.

What documents do they require, what credit scores do they allow, how do they verify previous rental history, etc.?

I was only thinking of outsourcing written communication through messaging as most of that is general inquires and 90% of those can be pre documented.

The other catch is you have to either document prior experience managing rental units or use a property management company if you need the rental income to qualify. 

Call the bank(s) and demand you are re-added to the bank accounts, document everything your partner has done with funds from the business account that are unrelated to the business such as buying vehicles. 

Im worried if I show them a written document that the old host gave them to me they might remove the other 5 in the other hosts name that I cohost...

While separate accounts sure helps with the audit trail, it's not necessary if you note the reason for a a deposit and withdrawal on the drafts or "source" document. 

How, or better yet, who should I go to, to document this transaction?

Crazily though, last week I got closing documents that had none of the lender fees - the closing company hadn't communicated with the lender in weeks and completely forgot there was a lender involved. 

You just need to close correctly and legally.We have several information and instruction documents we send out for free to anyone wanting to learn.I will reiterate -- no fight intended -- just advising what we have seen, done and developed over the past numerous years.Stay safe out there guysAlan