Read the fine print in the warranty.

I don't know the square footage .. but would be nice to see how much the square foot cost.

I would probably try and locate it near the blower so that it is less work to hook up and it would also be less easy to steal if it's mounted on the building or on a roof and out of reach.Looks like these units come with a 16 foot line set and it's $25 to add the brackets to mount the unit to the side of the building.  

I print off 20,000 letters, buy a ridiculous amount of envelopes (I guess that would be 20,000) and pay her to sign the envelopes, stuff and stamp them, and take them to the post office.

In any conflict of terms or conditions, that which is added will supersede that which is printed or marked.

If you are someone who lacks experience in estimating rehab costs yet you can reasonably predict ARV and calculate the discount you want to buy at, is there a method for doing a rough estimate of rehab costs such as using avg. rehab cost per square foot for your farm?

Printed out all pertinent documents from J.

You can just print the cards and hand them to the tenant.  

After 10 years owning my own printing business I decided to start real estate investing in 2015.

My suggestion would be to try to get on more stable financial footing before jumping in.