Any additional due diligence questions or red flags I should look out for. since its my first time to invest in multifamily3.

More secure and stable than an STR (also less competition) but you aren't in the red like you'd be with an LTR. 

Was it on yellow paper with red ink?

Both the daughter and Dad have excellent credit history but feel this is a red flag. 

They city will red tag it and require you to upgrade everything and get a Certificate of Occupancy before you can rent it.

Generally, your local, community, credit union will have best rates, local decisions and deep roots in the community. 

Heck go to the casino and put it on roulette wheel of black or red. 

You are disputing a condo agreement we do not have and we know nothing of your paint and vent beyond what you say.Regarding amending the lease, it can be a simple document you and your tenant sign stating that you are amending the term of the lease to be 2 years, and the tenant has an option to terminate the lease at 1 year.Regarding the bathroom, if it has a tub or shower and no other ventilation, I would go with the vent fan as the root cause.

She sent a reputable plumbing company out and they gave us a $9000 bid to do excavating, repairs, etc. due to some roots getting in some plumbing under the house.

MInut has a low average review (mid-3s I think) on Amazon which is a bit of a red flag. 1 per room at a total of $60/month sounds excessive for something that is not likely to be a common occurrence.