I’m pretty sure my advice is vague and not helpful but I’d lean towards keeping them and collect the late fees.

If you have funds and have communicated with the firm (after you’re the closed, winning bidder they’re usually happy to take your call), you can technically pay at any point that is convenient to them and you prior to that date and I know they have moved dates back in some circumstances before but don’t count on that. 

Depending on what you're leaning towards (multifamily?

If you want to use the heloc for speed and convenience you can always refinance the properties in the future and payoff the heloc provided you can qualify. 

I’d probably lean towards selling and reinvesting the money elsewhere that provides you much higher returns.

From reading a few other posts, I understand that the student rental market is saturated and hence I’m not leaning towards that demographic.

If possible the house may be paid off ahead of schedule.Seller X_________Purchaser X__________Upon signing of this contract the selling party will pay off the property in total & sign the deed via quit claims deed to the party of (my name) or associated company.Seller X__________Purchaser X___________The property is known by sellers to be free of any leans against it.

Since I attempt to buy and hold through the BRRRR method, I do lean heavily on finding the After Repair Value (ARV) through trusted comparable sales I get from a trusted real estate agent or I located myself of the MLS (multiple listing services). 

Purchase price: $413,000 Cash invested: $90,000 Property is conveniently located near all of our other assets.

I’m leaning toward multi-family home rentals investment, turnkey or rehab.