Review their applications and the screening process used to approve them as well. 

Do you have zoning permits, building permits, utility approvals?

I would advise you to approve this applicant unless there is a strong, objective reason not to - such as eviction history, a recent criminal conviction, or their income (including all disability income) is less than whatever standard you have used for all of your past tenants.  

They have been approved for a single family home Fannie loan (cannot do FHA because my husband works in the Cannabis Industry and the gov't will not allow).

Under no circumstance should a rent ready be quoted at 3-4k then invoiced at 6k with no explanation or approval.

We are allowing her to find someone to replace it and save money as long as they are licensed and we approve it.

Buyers if you want an extra advantage over other buyers call your favorite Mortgage Banker and ask for a "Fully Underwritten" approval not just a Pre-approval.

Private lenders offer fast approval and flexible terms compared to traditional banks 

They have been approved for a single family home Fannie loan (cannot do FHA because my husband works in the Cannabis Industry and the gov't will not allow).

I've been approve by the bank and they are willing to loan 80% of the money, but I need to come up with the 20%.