The house is in good condition. 

Now obviously there are going to be requirements/stipulations to doing this, so I highly recommend you find a lender that does delayed financing and can explain their terms and conditions to you.

If a landlord calls you for a reference and asks, "did they leave it in good condition and get all their deposit back." they want you to say yes.The biggest question is what benefit is there in returning money to them throughout the year?

Previous to renting it was just me and my wife and we did not use the air conditioning much.

The carpet and paint were 5 years old but both in excellent condition. 

Should we both construct and sign a contract stating the terms and conditions of the loan and any ramifications/penalties for not paying back?

The house has new windows, 1 year old roof, and the first floor unit was redone with laminate flooring in the kitchen and has the original hardwood floors (good condition) in the 2 bedrooms and living room.

Suppose I use friends/family money (Private Money Lender) to loan me 45-65K with the condition that I will pay them from the HELOC once I get it, how much interest is considered reasonable to pay them if I pay them back in 30-45 days?  

What condition was the comp in?

I'm telling you as a local that the property is worth no more than 75,000 in it's current condition yet it is being assessed for ~$100,000 due to it generating rental income in the last 3 years.