But mostly our household income has nearly doubled this year over last.

It doesn't seem like the father will stay at the property, and he is only applying along with his daughter so that their monthly household income will be at least 3x the monthly rental rate.

However, an exemption of more than $25,000 is not allowed to any one person or on any one dwelling house, except that an exemption up to the assessed valuation of $25,000 may be allowed on each apartment or mobile home occupied by a tenant-stockholder or member of a cooperative corporation and on each condominium parcel occupied by its owner.

Clark County has a limit of 3 dogs per household, unless there is a special permit.

The make up households can change over time for various reasons.

A true ADA animal is highly trained, and not likely to soil carpet, however, it is under the same jurisdiction for damages as a regular household pet. 

As others have mentioned above the household formation ties into everything too as do the laws.  

Those who have them want to stay on Section 8, and therefore make sure to pay their rent on-timeYou have more demand for your property, as you've opened up to Section 8 tenants.Cons of Section 8:Property managers (that I interviewed) complained about the number of people living in the household and the state of the property upon turnover.

There is no line item on a tax return for your household rent.

Is there a Head of Household arrangement or something else you have not told us?