401K Withdrawal or Financing?

[Michele Masters]

Looking to buy my 2nd AirBnB property for <$400K (singe family). I am considering financing the $112K due at closing with a HELOC and a 401k loan and get a $300K investor loan. This comes to a monthly outlay of $3,721 with a total loan costs of $284k.

I am 60 yrs old (no penalty withdrawal) and have no intention of ever retiring.  So given that, I am looking at my retirement funds (>$2M) as a possible source for funding.  At a 17% tax rate, my cost for the $482k withdrawal (includes tax payment) comes to $82k in taxes.  

Since $82k in taxes is less than $284k in loan costs, I think this is a viable option.  What am I not considering?