But, you'll also have other problems... most or all heavily regulate short term rentals... so if you can't cash flow with a long-term rental strategy, you'll be in trouble once regulators catch up with you. 

If you live in one unit and rent out the other, you can cover some or all of your mortgage and expenses with rental income.

Broadly speaking, there are two types; offsite (like SFR, small apartments, etc) and onsite (large apartments with leasing offices on the property).For offsite, I usually see 8-10% of collected rents, half or all of late fees and 1/2 to all of the first month's rent. 

And as @Jay Hinrichs says, the market needs to be right for this strategy and you need a little "jingle in your pocket" ;) Most the time you are bringing a seller current on payments, providing moving expenses, and tackling deferred maintenance/updates - or all three on sub to.

Since he is on an oral lease, just give him 30 or 60 days notice (depending on state) that his lease is not being renewed.

Wouldn't it be better to serve some kind of notice since oral notices aren't legal?

There is no reason you have to have it all done by this vendor or all done at once. 

Examples of short and long term uses, HELOCs & CES.HELOC(Short Term)- Use a portion or all of the HELOC now knowing you're going to pay down quickly, which eliminates payments and interest.HELOC(Long Term)- Many HELOCs have 10 year interest only draw periods, while CES have a P&I payment, HELOCs may have less impact on cashflow over the long term.- Perhaps you think rates are going to move lower.

I would rather spend some front end money now and do a relocation, then be able to use simple side-by-side units than to be forced into stackables or all-in-ones.

Verbal/oral agreements are not binding in real estate.