As for house-hacking an existing quad, only putting 5% down in this high interest rate environment will almost certainly mean you won't be "living for free" as is the point of house hacking.

Its just so hard in the current environment to get any cash flow with SFR (unless you bought when rates were lower or are doing a well-executed BRRRR). 

I would definitely get another quote for the work as that sounds high but would be a permanent solution in place with peace of mind moving forward. 

Hey Nick, I am a new investor here I appreciate your response to OP's question, could you elaborate on the complexities associated with assuming a mortgage in today’s high-interest rate environment?

Peace, love, and cash flow my friend

(Not to mention the regulatory environment has clamped down.

It is still possible in this current environment, however. 

HOA fees are rough for borrowing on investment properties in this interest rate environment too.

The best I know of (and we can do this) is 15% down, but even then in this high interest rate, high tax, high insurance environment it's really hard to get a property to cash-flow positively without putting a lot more down.

Part of that is the incentives our state offers to new business, part of that is a business friendly general assembly a regulatory environment, and part of that is our low corporate income tax rate.