Use the "extra" income to build a reserve for maintenance, vacancies, and other expenses that don't happen regularly.

If everything else checks out we ask for an extra deposit or advanced rent.

They see the lower rent and don't factor in the extra expense. 

At a minimum you can put your extra funds into a high yield savings account, or even better 4-week treasury bills that give you state tax exemption and keeps you liquid for your next acquisition.

Well, do they have a job to pay that extra $200 plus utilities per month?  

We do get a better fee/split structure, and that's a fair trade for the extra work of managing a large investor base and it's associated extra accounting and tax reporting overhead.I also find the advice in the OP to be contradictory. 

Consider how it will be used and if the floor can function as storage, rec room, family room, extra sleeping space, etc.From what you've shared, my concern would be the "hills" that may cause a tripping issue.

Do you have a full-time job already, assuming you have extra time, do you want to spend it doing another brain-draining task or would you rather spend it enjoying yourself?

You can lower the price.The buyer can pay the extra $9k in cash, if they have it.The buyer can walk away with their earnest money and you can lower the price $9k for the next buyer or require them to bring $9k in cash. 

Older people like this often need a little extra help with technology.