The people who are already working in that specific market will be the ones who will be able to give the best direct advice.

However, for two people being roommates, some privacy would be better I think...What would be the best way to somehow install doors or some kind of separation?

true people search is pretty solid and its free.

$300K should allow you to buy a duplex/2-unit and both doors should be offering a profit even at 15% down.If you are in a situation where you are getting hit with high taxes, high rate, low rents it might be a "Walk away deal".I have to have conversations daily talking people out of buying a particular home because its a bad deal.

Does it make sense? 

I'm from Stillwater Oklahoma and multiple people I grew up with have started reaching out to me on how I can help them or someone they know with different properties and lots.

This makes more sense to us than relying strictly on  rigid yes or no criteria where any negative  disqualifies a candidate entirely.Some criteria is weighted more heavily and can overcome negatives. 

House hacking is absolutely still a thing and many people have been successful with this strategy.

I never want to be the first to do anything. garbage deal let it go. you are talking about council variance, constructing or renovating a structure, you won't be able to get a permit. not advice but not to by the deal and not to look at the adu as anything but garbage anyone who says any differently should look at a zoning map and show me why and how an ADU makes any financial sense. you are only getting yourself into a very poor situation. tear it down and move on. 

Thought maybe people had experience with enforcing deed restrictions.The title company absolutely carries fault.