It took about 5 miserable years for the dust to settle and that is why I am hard on everyone who writes posts claiming they think they have everything figured out.

Question 1 when I find a deal how do I write the contract with the seller?

I delivered 30 day notice to quit mid March since it was not in writing.2nd floor had not paid rent since December 2020.I contact both tenants once I was on record as owner to let them know I would be coming by to collect rent.1st floor paid (there had been no previous issues with rent being paid)2nd floor ignored my request.

In this case, tell them (in writing) that they did not live up to their contract and you will not pay until they complete work as agreed.

That might be hard to know but I did write an article for Bigger Pockets on it that you can read HERE.

Some companies will write a 2 family but not a 3 family. 

If keeping the deposit was a condition of the lease break, you should have put that in writing.

If the seller doesn't have a realtor, you can pay an attorney to write up a standard contract for a lot less than that.

Is it possible to also write off the other common deductions (PMI, interest, depreciation) while living here? 

But you need that standard in writing and published and to follow it to avoid any discrimination issues.