(There are other ways to obtain/develop that evidence - such as using certified mail or my “practical advice” below.)In your case, because your friend found the letter inside the mailbox of the last known address, you now have specific evidence of having mailed the letter “…by first class mail, to the tenant's last known place of residence” - “Unless other arrangements (had been) made in writing by the tenant…”Again, in my (non-lawyer) opinion, you’ve complied with the letter of the law as to your concern - “Unless other arrangements (had been) made in writing by the tenant…”[Practical advice: Where I self-manage, in my “Notices” section of the lease, besides my physical address, phone numbers, etc for notices to me, I provide two email addresses for myself, and state in that part that email is my preferred method of communication.

I bet the filter is clogged 

Your best bet is definitely going to be a small credit union or regional bank in that area. 

Probably not a great bet.

If you want formalized training, your best bet is to take a course and then network like crazy to get in the orbit of other successful syndicators so that you can see how they operate.Here are some resources:Value Hound Academy with Craig HaskellSyndication and Crowdfunding WorkshopGene TrowbridgeJillian Sidoti

If you interacted with persons in trying to understand there quoting as you communicated here, no you wouldn't get much for answers because it's demanding, condescending and with hollow threats, nobody wants to deal with that BS or person so of course they blow you off, I bet you'd blow that person off too. 

If you can coordinate your purchase with the Menards 11% off Rebate Match that is tour best bet.

If they are filing false complaints it’s one thing but if it complaining and it’s true, even if it’s minor in nature - that’s more an Airbnb issue and they know how to game the system.Reality to is if you get them to stop whose to stop them to ask a friend etc.Your best bet is to talk to them and find out what the Cruz of the issue is

Back o the original question assuming the 1st loan will allow a 2nd smaller local banks will be your best bet or a true Private Lender.

No one knows what the future will bring, so I would not make an all-or-nothing bet on refinancing in the next year or two.