@Ellis Moyewe really don't know a lot about this situation since there aren't many details in your post... but i don't think this makes any sense for anyone involved here...if it's a flip that's not selling, refinancing may not solve your problem and allow you to pay back the HML in fulland typically a sub to buyer wants a low interest rate... and if you refinance now you won't be getting a low interest rate, you'll just be getting whatever the market offers.and finally.... the vast majority of loans are NOT assumable. 

While I have none in this market I have been on one realtors monthly newsletter with market analysis for over 8 years. 

Far too many get stuck in the "paralysis by analysis" stage, thinking they just don't know enough to get started.

Recently, our real estate agent did a market analysis and estimates we can sell for between $575K-$585K, resulting in a net gain after all of our fees of about $100K.

Our analysis is ARV - Rehab estimate - Finance Costs - Holding Costs = Profit.  

Start running deal analysis on properties during this time. 

We gave a final offer of 417,500 and closing costs, and they accepted.Currently in the middle of new floors, a new bathroom, new kitchen lay-out, new trim—after completing tons of demo.

She tends to take several days before she finally requests a contractor to go out and see the property to make a quote, and then another week before the contractor submits their quotes.  

You're at the net worth level now where detailed investment and tax analysis can have large impacts to your overall ability to retire and spend. 

Finally, work with your lender to assess the financials thoroughly before jumping in.