Additionally, don’t overlook the opportunity cost of pulling money from your 401k—those funds could have been compounding in the market.I’d also suggest stress testing your ROI by running scenarios with higher expenses or lower rents to see how resilient the investment is.

+1  Real Estate Investing Data and How-to Guides - This here shows that you can filter to Multi family but I don't see it as an option as well.

What percentage of sellers are still contributing in some way, do we have data or knowledge of this?

And if your selling NON mls props its hard to run data..

and usually take the state test to get the license and skip the federal part of the test ..

Looking for guidance on options. new builds aren't hard to finance and I would argue they are preferred to existing fix and flip loans, especially if you have experience. banks look at your experience, your builder's experience, loan structure, permits, etc you need to get an experienced builder familiar with advanced underwriting and negotiations with local, regional, and national lenders. in columbus we do ground up construction for clients at a 20% discount so they can BRRRR out of the new build with equity and we have pages and pages of data on what we build and why and it's all supported by market statistics. 

If you use niche.com you can pretty easily find median home values, median incomes, an some data pretty easily.

Now is not the time to “test the market” with an ambitious price to “see what happens.”

Did you only remove the drywall and flooring and not do any testing? 

You should check if the bank feeds work with your bank otherwise, it's a deal breaker unless you don't mind manually doing the data entry.