Of course we simply add on say +5% for waste when originally purchaising and return the rest lol.

Here is my grand prediction, to add on the Mr Morgan.  

Using existing properties already correctly zoned and building a small cottage or add on apartment that will rent for a reasonable amount.

Once you've determined that vacancy, calculate that risk over 6 months to assure your revenue is covered.For example, if you expect an entire month of vacancy then add on $275/month. 

I'd send them a formal notice that your insurance does not allow pitbulls , and that they have to get rid of it.But, you really don't want to lose your paying tenant right now, so after you've sent that notice, I'd let it be, until the courts reopen and you can let them know more firmly.You can always take the pet rent/fees out of their security at the end, assuming that these perfect tenants don't also leave you with unpaid rent, and damages.Another thing that you can demand is that they get their own insurance policy on the dog, with their renter's insurance (it's a pretty cheap add on to their car insurance, in many cases, although I don't know if their insurance is going to cover a pitbull).

To add on to @Sue K.'

Its not part of their rent, it was an add-on.  

If there is not a clause in the lease add one.  

This allows you to add on to the principal, in my jurisdiction at least, the costs of going through with a Bill in Equity or a Writ of Fieri  Facias.

I personally would not add on to that dividing wall.