I would love to help your family find the perfect home. 

In a perfect world I would have had a GC give me a quote before I made an offer, but in this case, I was only able to get quotes after the property was under contract.

It seems to me that even in the perfect situation, where I get paid like 12% interest rate with no chance of default, and I get a HELOC with around 6% interest rate, I'm going to have to pay taxes on the interest I collect, but I cannot write off the interest I pay, and it will probably not be worth it.

There is no perfect property.

I have found a condo in my area that is a perfect flip but my math says I need to get it for $65,000 max and the property is listed at $115,000 and the ARV is $128,880.

Hard Money takes 3 weeks if everything is buttoned up and perfect.

Just choose your partners well and don't move too quickly until you are certain you have a perfect match.And I could see where a long-time management company relationship could one day grow to where the management company is making a financial investment in your acquisitions (alongside your other investors).  

Also, realize that IF you are able to find and close on a $100,000 house you will have repairs and other expenses, plus the perfect tenant will not show up the day after closing.  

You are in a perfect place to house hack. 

@Tarik Turner that sounds perfect for my strategy we'll have to talk about that.