We even had a serious "bite" that almost moved in earlier this month, but didn't sign the lease.So my question is, since we are about to enter the worst time to get people to move (holidays).

First, you should have a iron clad signed agreement with your property manager for everything.  

(not so important but if they only require 15% down on a single family home that is usually a good sign that you are working with a flexible lender) Can I change title to my LLC?

It could just a joist issue which isn't an expensive fix or something to worry about.Check the ceiling for brown spots as sign of a current or prior leaking room.Window units in house means there is an HVAC issue no matter the reason given by the owner. 

When touring an investment property, what is one thing you look out for that if you see it you immediately WALK AWAY? 

certificate of occupancy, I had to pay for all new exit signs while I was in contract.

Since I can't include expenses for my unit for tax purposes, I'm wondering how I should handle accounting for my unit.Should I pay rent from my personal account to the business account and then let the business account handle ALL transactions related to this property?

I own another house, it was a live in flip, I bought it when I was 20 years old and my father co-signed because of my lack of credit. 

Draw it up in writing and have A & B sign it.

#3 I signed a 6 month rent guarantee with this TK/PM company and when I made mention of this they said yes you're right if no rent is paid by end of month we will definitely pay you full rent(Why wouldn't they make me whole on the 15th and try and collect from the tenant to reimburse themselves?)