In fact they are responsible for the duration of their lease or until you have it re-rented.

They stay in a hotel for the duration of their stay.

You need to know what you value in your current situation.Values such as: Price for quality in labor and material, or If holding costs are an issue perhaps duration to completion.As far as quality goes, do you want the 'Best of the Best'(out of your options) for your investment, or is mid-range quality OK.

I don't know if I'll continue to use them after the duration of this lease.

Is that 7.5% +300 per month or 300 per month for the duration of the loan with 7.5% per year?

Unless you're planning on significant appreciation or rent increases this is likely a loser, although ultimately I would decide based on the potential internal rate of return for the duration of the investment, to see whether you can invest that money for a better return elsewhere.    

I pay her mortgage  throughout the duration of the flip($750) and pay the house off at the end ($64000). then profits mine. the ARV should be around $110000 to $120000 after a $25000 rehab. 

Byron the lease duration; year, MTM etc seems very influenced by location.

Wouldn't the prior leases no longer be valid once the property has changed hands, regardless of how long until their former renewal date or the stated duration of the old lease? 

I am curious if any city in San Diego county allows ADUs in non owner occupied properties.References are below:San Diego: https://www.sandiegocounty.gov/pds/zoning/formfields/PDS-611.pdfOwner-occupancy of one of the dwellings is required for the duration of use of the ADU for residential purposes.