If you already have a private lender lined up, a simple letter from them stating they will back you for the loan should suffice.

I'd need a new permit issued if I was changing the use or having major work done, but otherwise the permit issued many years ago to a prior owner suffices.

A short explanation of the reason should suffice. 

Ou residential agreement had a clause that stated two or more late payments within 4 months would be a violation of the agreement. i issued a letter to them last month informing them any further late payments would result in termination of the lease (which is now on a month-to-month. my question is, did my letter specifically have to say "notice to cease", or does explaining the terms and consequences in a late payment letter suffice?

Unless this is a large multi-family, a spreadsheet should suffice for your first year. 

Suffice it to say, it's a good idea in theory but a lot of people end up exactly where they deserve.  

Is in person better to make connections or will online suffice?

I have had it happen to me.I don't want to explain in detail what crooks do as we know there are nefarious folks who troll these sites looking for ideas.. but suffice it to say there is a bunch of fraud that goes on that us honest guys don't see but title companies have to deal with

Lastly, what about rental agreements can the existing owner rental agreements with tenants suffice or should I execute new ones? 

For practice purposes, yes, (conservative) guesses should suffice.