I hope more investors come to his area and fix that entire corner.

This is largely due to the fixed nature of ongoing maintenance costs, which become proportionally more impactful as the park size decreases, thereby inflating the expense ratio.

I also agree that RE appreciation is unlikely to match the last dozen years, but you never know.Where I am unsure we agree is that paying $450k to improve the cash flow ~$3k (your numbers but I expect my delta wold be similar meaning both my cash flow estimates would be worse than yours but both would be worse by the same amount not affecting the difference) makes sense especially if the cost of having the extra $450k is only 6% rate which is historically simple to beat via numerous investment options and hopefully no one is investing in RE for an expected of 6%.  

Once you fix it up, you could refinance to pay off the HML.If you do it right, you should have enough sweat & forced equity to have 10-20% equity for the refinance.

Id like to understand what the most profitable way to fix up a current 1,700 SFR in a 6,200 sq. foot lot would be?

Starting with a smaller property or a few fix-and-flip projects can help you build equity, gain credibility with lenders, and better understand the process before scaling up.Securing funding for larger projects can be challenging without prior experience, but options like hard money loans might be worth exploring.

It's called a payoff statementif it's a big lender you will not buy the loan as it will take forever, you are better just paying it off. you then can foreclose based on the total balance owed to you which is both loans and any accrued interest. regarding fixing property or selling as is, that really depends and needs to be evaluated on a case by case basis 

@Kevin Wood: Fixed Asset Management module is included in the QuickBooks Accountant version where you can calculate the depreciation.

You will owe monthly payments until you fix the property up, rent it out, and refinance to a more traditional 30 year fixed rate product. 

I purchased sub2 a handful of times for fix-and-flip types of situations, where I was in and out of the deal in 3 months.