I've done this for a few clients, and my ops director does this for her personal property investments that are all held in different entities/holding companies, so it can be done!

Before you invest in cost segregation, you need to figure out whether it will help you.

Office space is gutsy at this time with many companies working remotely, maybe part of your investment was to bet that people will be coming back to work in person.  

You came to the right place to learn more about real estate investing!

Partner B will get $220,000 + the single wide, while Partner A's heirs will get the apartment building and the double wide.They intend to sell one property ( the double wide mobile home ) and use the proceeds to either pay down the loan or reinvest in another rental property (possibly in another market).To defer capital gains tax, they plan to use a 1031 exchange for reinvestment.Goals & Challenges:Tax Efficiency – Structure the transfers and payments to minimize tax liabilities for Partner A’s Spouse and the Children.Guaranteed Income for Partner A’s Spouse – Ensure a fixed monthly payment of $1,100/month while transferring ownership to the Children.Long-Term Investment for the Children – Build a solid rental portfolio to support future financial growth.Operating the LLC Under New Ownership – Ensure a smooth transition, including removing Partner A’s Spouse and Partner B from the LLC structure.Proposed Plan & Questions for Advice:Instead of outright gifting the 50% interest, the LLC will be restructured so that Partner A’s Spouse retains a Preferred Equity Stake that provides them $1,100/month in priority payments but gradually transfers ownership to the Children.Payments will only be made when rental income is sufficient (i.e., when rent increases to $850/unit).Partner A’s Spouse is willing to forgo payments in bad financial times but wants assurance that they won’t face any tax consequences on unpaid amounts.If Partner A’s Spouse passes away before full ownership transfer, the Children inherit the shares at a stepped-up basis (avoiding capital gains tax).Questions:How should the LLC Operating Agreement be structured to allow withholding payments when necessary without triggering tax or legal issues?

You'd still want to evaluate the DST as an investment option of course. 

Due Diligence is Critical—Don’t Waive Inspections•Since this is your first investment, make sure you follow a solid due diligence process before purchasing.

In the new state where you intend to invest, research real estate valuations, trends, and neighborhoods.

I can see why you want to invest out of state if that is your budget. 

ADU construction is not 1:1. meaning investing 250k into your property by ADU will likekly not increase your property value by 250k.