Get an acceptable offer and include in the contract your ability to extend close for up to 60 days.

At the worst, by taking the note the seller is going to spread out the tax on gain for the duration of the note. 

The other alternative is at maturity you extend but then have to pay an extension fee of 1% - 3%. 

Usually they lend out their own money at a shorter duration (6 - 12 months, on occasion you may find someone willing to put their money to work for 5 years but usually nothing further than that).  

I live in Norther NJ and I was able to find a single family home with an extended family suite (4bd/2ba) to house hack.

Typically Id say this is best done after 5 yrs but there are a number of factors that can cut this to one year or extend it beyond 5. its all about the purchase, The money you make will be made at purchase and the money you lose will be made there as well. 

And they're already talking about extending it past march.

Our tenant is moving out in a few weeks and we are worried that this will cause us to lose rent for an extended period of time.

Mostly in the Studio City/Toluca Lake extending into Burbank area?

For example, in the standard California Association of Realtors lease, it says the following:Lease shall terminate on________ (date) at _____AM/ PM.Tenant shall vacate the Premises upon termination of the Agreement, unless: (i) Landlord and Tenant have in writing extended this agreement or signed a new agreement; (ii) mandated by local rent control law; or (iii) Landlord accepts Rent from Tenant (other than past due Rent), in which case a month-to-month tenancy shall be created which either party may terminate as specified in paragraph 2A.