So if I understand this correctly, by qualifying to extend the 5 year rule to 10 yrs, $250k if single or $500k if married of proceeds from this sale would be exempt from capital gains? 

Key Details of the 45L Tax Credit:The credit offers up to $2,000 per eligible unit for builders and developers of residential homes that meet specific energy efficiency criteria.To qualify, the units need to meet or exceed certain energy performance levels in comparison to the national model energy code (e.g., the 2006 or 2009 IECC — International Energy Conservation Code).Cost Considerations for a 90-unit or 112-unit Project:The actual cost of qualifying for the 45L tax credit depends on various factors, including:Energy Efficiency Compliance: The primary cost will come from ensuring that each unit meets the required energy efficiency standards, which typically involve energy modeling, certification from third-party energy raters, and potentially upgrading insulation, HVAC systems, windows, and other components of the building to meet the necessary performance levels.Energy Modeling: Typically, you'll need to pay for an energy consultant or engineer to model the building's energy performance and ensure it qualifies for the credit.

I used to train up there when I was in the AZ National Guard and my wife and I met there in 2015.

With everything paid off, they’re looking to slow down but are hesitant to sell due to capital gains considerations.Purchase Price: $1,750,000.00Downpayment: $400,000.00 - Will do a 1031 - Selling two of my SF properties for the downpayment (bought for 120k + 146k back in 2017 & 2015). 

The only tie is really has with Chicago is the state capital being there.

@Denise CarringerMy preference is to go local - some community banks offer this type of service or local escrow companies, which is what I found, because they offer a higher level of service than most national.

We vetted a  handful of "turnkey" companies and REI Nation was the best in terms of reviews across multiple sources. 

They are also useful for private phone conversations and could be used for storage of valuables as they could be locked.I'd love to be able to broach this idea with other nationalities and cultures but it's really hard if they're not working very long hours and have hours of free time at home.  

Just to complicate things further, a capital call has been issued.  

At its most simple we’re separating the appreciation/capital buildup benefit from the cash flow benefit.