USPS shows that the letter was delivered.

In New Jersey, must  you physically deliver NOTICE TO QUIT AND DEMAND FOR POSSESSION AND NOTICE OF RENT INCREASE to the tenant or can you mail it?  

Your buyer's agent will meet with the listing agent to get the keys and either get them to you or deliver them straight to the property manager.Congrats on the new purchase and happy investing!!

I've heard of mentees that started out cleaning up construction areas on a flip at the end of each work day or picking up supplies at Home Depot and delivering them to the job site.

I've heard of mentees that started out cleaning up construction areas on a flip at the end of each work day or picking up supplies at Home Depot and delivering them to the job site.

The building was supposed to be delivered vacant yet seller did not do their part and I ended up with roughly 8 tenants. 

There are other reasons why people prefer to have mail delivered to another address, not just because you'll no longer be living there.

@Anshul Jain Unless the lack of rental income from the tenants while you rehab would really be hurting you financially, I would plan to deliver all 3 units empty.

You need clear communication with the Tenant and with the Property Manager.The day you take over the property, deliver an introduction letter to the Tenants.

As far as my personal adjustments for my flips are going after smaller, less expensive homes in which I can get in and out a bit quicker which helps deliver some cash flow from quicker flips as opposed to the multi million dollar stuff I had been doing (still have one ongoing).