@Brian Murray a lender would be best equipped to handle this question, but for most secondary loans (Fannie/Freddie) that I've seen you'll need to go FHA to take advantage of lower downpayments with an owner occupant situation. 5% down conventional is typically single family residences.

New guy arrives, sees weird equipment, doesn’t know how to fix it.

Your friend should be worried because she is not equipped to manage her property.

If it was a $1800 piece of equipment, I may be more careful, but what good Is a tool I don't have access to when I need it? 

If you use the personal car, make sure to keep detail record so that CPA can prorate the expenses between personal and business.19) Any equipment you rent for the rental business.20) Mortgage interest and property taxes21)There are many others and depends on specific situations.22) home office: Also, If your home qualify for a principal place of business for RE activity, any mileage to any rental property is deductible.If you are expanding, talk to professional.

My buildium software makes it easy for me to charge water bills so I don't need a billing company.I did not want to use a submetering company with provided equipment that charges a each tenant a surcharge depending on the level of service that they provide.

The problem was the postal sorting equipment was turning it into a nice suspicious white powder. 

About 2 years ago, I decided to quit my job operating heavy equipment, and decided to go to school.

I believe this approach is more cost effective from an installation and equipment standpoint.As far as heat pumps are concerned I thinks its highly dependent on what part of the state you are in. 

You may only charge for contracted expenses, rented equipment, material destroyed, items replaced and actual cleaning expenses.