Also relevant (and maybe deserving of its own question) -- my neighbors currently own five of the building's six units, and so I think will have to time the sale so that it happens concurrently with the sale of another unit (I'm foggy on the rules here, but it relates to buyers' abilities to get a mortgage). 

I have three deals going concurrently so my funds are otherwise deployed.  

I think the AO Smith unit that is still going strong can do 2 baths concurrently and I have never experienced it being underpowered (it is in a 2.5 bathroom unit). 

I now am going to run 3 deals concurrently and I am about to get really busy!

I put a duplex under contract that I intended to keep forever, but a buyer came to me for a quick profit and we are going to a concurrent closing. 

I happen to have a mortgage on my property though and would not want to transfer title without the concurrence of my lender.  

Concurrent ownership is when two or more people hold title together.

I want to be approved for building permits to build a new 3500 sft house on the 10,000 sft lot while concurrently waiting for approval for the subdivision to happen.

From what I understand of your situation a 1031 is a no-go on every front: your current prop is your primary residence, you're not looking to purchase a new prop for a while (1031s exchange properties concurrently, you can't sell one and then buy the new one a year later), and your new prop would also be a residence.However, the bonus of your current prop being your primary residence is that you'll likely pay no taxes on the sale since you've lived there for more than two years.

NOTE: The Periods of Ownership and Use of the Home Do Not Have to CoincideThe requirements for ownership and use of the home may be satisfied during non-concurrent periods so long as both of the requirements are met during the five-year period leading up to the sale.