You are only required to have the property be your primary residence for 2 out of the last 5 years. 

Imagine a $2M loan not requiring a down payment.

For the tenants that will occupy the empty unit in the not too distant future I can make my own rental agreement, in particular, I plan to let them pay for the water as well, and I will set a reasonable security deposit.But for the tenants in the currently occupied unit:1) Would it be possible to write an addendum to the existing rental agreement to require the tenants to pay for their portion of the water bill?

You are not EVER required to use a property manager if you own more than one property, or for any quantity of properties you own.

This is implicitly required of any HML.

Does it require partners or can you do it on your own?

Just on the business level for landlords to be as specific as possible with their requirements and give detailed line item dispositions. 

And actually, there is no statutory requirement that you rent the property. 

1007 required?

Yes, interestingly in NJ the stove is required for a home (no other appliances are required).