However, the loan could still impact her indirectly.

If you co-sign, the loan will consider both your incomes but also both credit scores, so her credit could impact the terms or buying power.

The disparate impact standard is a wrinkle, but I imagine that will end next year. 

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This is where a sale may benefit you long-term if you can find an investor to take it before the increased rate and pending rent decreases impact the value of the property further.

I  started keeping an event journal to remind me of issues or unique incidents that impact the income/occupancy of each property, including maintenance block-offs. 

Assuming the insurance premiums don’t significantly impact my cash flow (which is one of my primary goals), how do you assess the risk of taking out a loan under my personal name versus opting for a commercial loan that requires a larger down payment and comes with a higher interest rate?

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I don't know how much the $ impact is of your rate increase, but how much are you increasing rents?

.- Most people kept their ADUs under 750sf to avoid the impact fees- For subdivision, it wouldn't be applicable in your case due to your lot size.Feel free to reach out if you like to discuss in details.