If you purchase the house, though, why would the former owner have any say in those decisions?

So, you are working through 2 decision makers, not one.A Realtor can really provide you value in a transaction....especially your first one! 

I can sell it at any time for a profit, so I'm hoping to let it run and pay for itself for a while before we make another decision on it.

:This is all great news, we need more housing units in our markets and the local level politics seems so hung up by NIMBY'ism that local leaders won't make decisions for fear of retribution.

So I just need to make a decision and go with it.

You want an accountant who can help you strategize and who is responsive when you want to know the consequences of the financial decisions you are making throughout the year.Good luck.

There's no clear-cut answer IMO, it's a personal decision.  

What decision is your significant other leaning towards, what stress is in your relationships?

in a vast interview process with many steps before allowing someone to move in. a new roomie is an everyone-decision, not a landlord-only decision; if you're expecting people to co-exist in a space together (for longer than just a few months), you have to make sure they all have some things in common, or at minimum have the right expectations in terms of cleanliness and routine habits.someone working the night shift and someone else having a 5am rise-time, or someone who works from home in a call-center job is not going to jive well for example. and someone who doesnt handle conflict well is not going to jive with someone who is brutally honest and up front about issues. happy to go into more deets on how we do things if it will help. this can certainly be lucrative in terms of cash flow, but there are huge mud puddles i have stepped in over the years which i have had to learn to navigate.

These are weighing on your decision.