I would prefer to lend at a slightly lower rate to an experienced and successful flipper with strong financials verses someone who just started out in real estate.

You can start with less, but the lower you go the more you're gambling with your investment.

"Sprint" - put 50% down payment + 15y mortgage, get less properties - but pay less interest to the bank as well (lower interest rate + higher equity gain ratio per loan).

They are all lower income C neighborhoods where there is pretty good cash flow. 

Do they ever accept lower offers if paid in cash?!

I was wondering if there was a way for me to take over his HELOC to have a lower monthly payment or if there were any other creative financing methods that someone could recommend for my situation.

If not, based on the prior bills being lower despite occupancy, it would seem I was unlucky enough for a leak to start within days of closing.

If you are in a lower price range, tenants may have a harder time buying their own fridge but the rental market is really hot right now and I would expect that you could easily rent without it. 

If you are willing to shell out an extra $1k/month to pay it off in 5 years just save the money and put a larger down payment down to lower the payment.

In other words, if it looks like a typical finished basement out here then expect the lower number.