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We only needed to pay earnest money and a portion of the closing fees bring upfront investment to 12-15K.

What costs/fees should I look out for?

It sounds like you've absorbed a bunch of problems already and a new sewer line and the current basement situation will cost you way less than the $50K in fees to sell it. 

It may sound nice to pay a 6% management fee but the extra fees can add up to be more than the other company that charges 10% with no additional fees.

I was studying the market and my rent will be just enough to cover the mortgage and HOA fee now I might to pay out of pocket for insurance but don't want to sell it yet because the area is growing and might have good appreciation in the years that follow.

@Shmou N.ShmouYou can collect Rent and all other fees; Utilities, parking, or any other fee needed.We don't currently have a notification of the deposit but I will add it to our develoemt roadmap and you will see it in an update.

The PM had a plumber go to the house, incurring an after-hours emergency fee, but was unable to assess the exact cause of the issue at night, stating it's either a frozen pipe or pump issue and they need to return during the daytime to fully address.

Wondering if it will be a waste in fees paid to either HELOC or Cashout Refi because there may be a possibility of having to sell to get the primary residence we want next year and end up paying Realtor fees to sell it. 

Can easily get a 20% referral fee just for sourcing and handing off that lead.