The underwriter suspended it, and dressed me down, saying that giving the investment property interest rate to someone currently living at the property in question was abusive and predatory (the UW assumed it was my idea).

Do I need to tell every applicant why they're denied?

They are trying to push a pet on you, deny access and sounds like other things.  

The two outcomes I could predict is either they say you and the seller tried to defraud the government or you committed elder abuse and tricked seller out of the property.

This is the simplest method, but it also means your tenants are more likely to abuse the utilities by leaving windows open with the heat or A/C running, leaving lights on, ignoring the toilet that constantly flushes on its own, etc.3.

For instance, if you have State Farm, even if the roof is absolutely battered and the shingle discontinued, they know you have no recourse in the courts in Illinois so they'll deny the claim and then drop you at renewal.

Hello,Inspite of sending repeated requests my tenants who will be moving out soon have been abusing the centralized AC so I wish to introduce a process in my rental where I as a landlord am in control in setting the thermostat limits for my future tenants.Are there any specific thermostats which will allow me to program high and low limits on the thermostat the tenants can't bypass.

When you finally sell the property, you can then, at that time, deduct those losses.These are the Passive Loss rules, which Congress set up to curb some pretty wild "abuses". 

Partner B is not on the loan, this way partner B can secure a 10% down second home loan in the future without being denied for having a property in the same market already.

Check around furnace, water heater, pipes, air filter, attic space, crawl space, garage, or whatever.If you see neglect or abuse by the tenant, don't address it in person where emotions can get in the way.