The property is currently managed by a third party (not the seller), and I plan on self-managing.  

Here is the language that I was given by my agent to use in the contract:Notwithstanding any other provisions of this Agreement, the parties agree and acknowledge that in the event either the Buyer, Buyer’s lender, Seller, any of their respective service providers, government agency or any other agency becomes the subject of a voluntary or mandatory COVID-19 virus quarantine or closure prior to or at the time of Closing, or if Buyer or Seller is the party to another transaction that is delayed as a result of a voluntary or mandatory COVID-19 virus quarantine, that results in the parties inability to perform on the Closing Date, the closing may be automatically extended by either party for a period of up to ten (10) business days after such quarantine or closure order is lifted, up to a maximum delay of thirty (30) days unless the parties otherwise mutually agree to extend the performance date further.

So... a little late  to the party. 

If the seller or you wish to push that date in the future than an addendum must be signed by both parties.

Contact your state congressman, this will be bad for all parties involved and tenants who do not understand this will inevitably be evicted at the end of this ordeal anyways.https://masslandlords.net/ten-...

Upstairs tenants admit they aren’t “parties,” but sounds like they don’t want any visitors at all at the house.There are shared spaces- front and rear entries and laundry facilities in the basement.

You should understand it completely, and it should protect both you and the other party. 

However, Person B agrees to manage the property until ~year 3, when person A + B jointly refinance.Additionally person A + B will enter into an operating agreement which binds both parties to these conditions and offers 50/50 equity in property.How do we structure this legally while minimizing the liability, in absence of a LLC.Side question:Are there different lending rates between a LLC and an individual?

If you don't want to devote a lot of time I would recommend getting something that doesn't need a lot of work unless you want to hire a 3td party project manager.  

Bailey, 460 Mass. 327 (2011)"[T]he Housing Court has jurisdiction to decide the validity of a challenge to a title, raised by a former homeowner as a defense to a summary process eviction action by a party acquiring the property pursuant to a foreclosure sale."