., owners of the entity can manage the property, use a power of attorney to appoint a third party to execute on entity's behalf, etc.. 

Unfortunately MD passed within the past 10 years a statutory scheme requiring third parties to accept what appears to be a validly executed, notarized and witnessed instrument... so if they insist we must accept.

Regarding the seller wanting to stay on for a year lease after closing I'd ask for one year of payments to be escrowed from the seller's proceeds with a 3rd party.

During this process we spec all finishes/fixtures/scope of work, and then provide a final "guaranteed" budget that will only change if hidden conditions arise (code/safety-related), scope of work changes (additional work added above the defined scope), or fixtures/finishes change (price will go up or down, based on the new selection and any re-work necessary).I strongly recommend you find someone with a similar process, who also freely offers up proof of licensing, insurance, 3-party reviews, and client references you can contact.Finally, if it's a long term play and you don't mind spending the money, consider the "phased" approach mentioned by @Nabil Suleiman.

It's a duplex so you'll have 2 parties paying $2-$2.5 each, I'm assuming.

There is one IRS-approved method for building or improving that uses 1031 funds.Construction 1031 Rules and Process In a nutshell, it goes like this:You go under contract to purchase the replacement lot in OklahomaA 1031 company creates a brand new LLC to act as holding company (Exchange Accommodation Titleholder)You enter into an agreement with 1031 company outlining your plans in the construction exchange You assign the purchase contract for the lot to the new LLCYou arrange financing for the LLC to purchase the lot (this loan can be from you, a third-party lender, or your 1031 sale proceeds)Loans to LLC is secured by Note and Deed of TrustLLC buys the lotNow the LLC can begin paying for improvements to construct the barn-condoDuring the building period, LLC rents back to you and makes you "Project Manager" to oversee the improvements.Once improvements are completed -- or at the end of your 180 days -- 1031 company assigns ownership of the LLC to you. 

It's good to keep this idea in mind, but for all intents and purposes, assume it'll be slightly lower than the ARV would be safe.The tricky part is, even if there is high demand on the property, what lender would go for paying 30K above the appraisal and project ARV?

I think for the most part is the concept of stopping time. 

The QI must be an unrelated 3rd party whose only function is handling the client's 1031s. 

But if Roth Inc were owned by a completely independent party, Taxpayer Incorporated would have no reason to pay commissions to Roth Inc.