Paying down your mortgage is 100% risk free. 

This will be my primary residence and my partner will be paying some portion towards the monthly expenses.

Not a problem for one QB Desktop subscription, but after I added it up, including one $200/month subscription, we would have had to pay nearly $5000 per year in QB Online subscriptions to match the capability of QB Desktop!!!

Quote from @Lucas Hunt:  I will essentially be managing the entire property/collecting rent and my friend will not have to lift a finger.No offense,  but your friend would be better off buying the property for himself and paying a PM 10%.

I like that the HELOC functioned more as a credit card, and I only had to pay for what I used, so I had 200K of equity on hand, but only had to pay the interest on 120K.

I'm just gonna take the specs to local engineer or architect pay whatever consultation fee and have them review it.

Not only that but you are going to carry a Heloc in a 2nd lien position and you will not be able to pull out more cash unless you do a cash out refinance to pay off the previous Heloc and take out more cash.85% of the home owners who take out a Heloc refinance in 3-5 years so it makes more sense to simply do a COR and avoid the future closing costs.

We even said we'd pay more. 

Buying a home is the best Investment you can ever do, owning your own home, having the equity and most times its cheaper than rent.How do I overcome the rate, by paying the principal down!

I purchased 2 homes from Bennah Oaks almost 3 years ago, delivery was supposed to happen early  2022..