Then sand down the hardwood floor, stain the wood a darker color to hide any remaining stains, followed by locking the odor in with polyurethane.

It doesn't necessarily hide it from the bank, because they will see your HELOC and know what balance is sitting on the account.

Not a fair system to sellers and can lead sellers doing patch work/hide problem they dont wanna fix and DUMP THAT PROBLEM ON YOU.     

Its like the difference between hiding behind a bush or curtain vs. a masonry wall.  

The best thing to do is be 100% upfront with the lender and hide nothing.

welcome @Dejan N. glad you came out of hiding!

1923 meets 2023.It really depends on what you need to offer to get renters in the area and what you want to offer and have in your portfolio.A little paint, hiding those wires and getting those antenna on a pole in the backyard would make for a fresher look too.Good Luck!

Transaction from A to B is not at arm's length, if he presents that to a lender as a purchase, it's mortgage fraud if he hides the fact he has interests on both sides.

Is there anything I can do to hide this?  

That  is either not an honest applicant & trying to hide something, or  is not an individual  seeking a win-win relationship.