Don't ask forgiveness, ask permission with them.

It almost sounds like you are asking their permission.

I gave her permission due to the fact I wasn’t paying for it.  

Those who are unfamiliar with the legal concept of intentional owner abandonment, will likely question the morality of renting real estate one does not own or have permission to use.

Previous tenants had dogs and installed a fence with permission (they did a bad job, and rigged the fence together with zip ties in some areas, but the fence still functions fine).6.

I don't know what the process would be like to turn an existing structure into a boarding house--but I'd imagine, your larger problem would be with existing zoning, which likely would not permit a boarding/rooming house in a zone where you currently have a single family home.The state maintains information about rooming and boarding houses here: https://www.state.nj.us/dca/divisions/codes/offices/roomingboarding.html but your municipality will have its own zoning laws about what is permissible.

If they are selling 30/60/90 info and you are not an institution with a permissible use provision, both you and them potentially run afoul of some pretty stiff rules/laws.

Can I sent a letter and enter the property without renters permission? 

@Mark Frattini the fact that they brought the dog in without permission is a lease violation and I would request formally that the dog be removed or they move out.

It's this:Find properties with basement apartments or carriage houses out back.Get a long-term renter in the smaller of the spaces.Because tenants are allowed to Airbnb their "primary residence" (which is considered the entirety of that property) with landlord permission, the tenant gets the license and makes you a co-host.