I do think you need a separate entrance option or at least two entrances in a four-plex to make it easier on the LTR tenants, but if you are open about it form the start, everyone gets it and you choose the unit composition based on which ones will be STR or MTR.

Is it possible for her to buy the house/land then we subdivide the property (property has an approved preliminary plat for subdivision into 2-3 separate lots, electrical and pluming lines have been put in place for future development).

What separates the 2%...... 

Doing a short term rental in a separated area that has its own designated, kitchenette and bathroom, would likely give you better returns and less headache.

Also, are you doing separate loans, or one loan covering both properties?

The numbers I use for an STR and long term are different so I would probably analyze them separately and then put it all together.

Send both and separately and use certified USPS. 

I use this feature for separate accounts for each property that is under the same LLC.

Does it have separate meters?

Estimate utilities and figure out who pays them (separate meters, landlord paid, etc)5.