Establishing good relationships with a few portfolio lenders will allow you to scale your business to another level.  

If you can meet the debt to income and get to 10 properties, I have respect for you!

It will give you the opportunity to establish the usable life expectancy of all major systems/appliances.  

I'm interested in doing this, but I need to establish a network of specialty contractors to bid jobs.

That trust can be the keystone of a very respectable fortune without actually showing up on my "personal balance sheet"."

Do one deal with the private lender so you can establish a relationship with them and if needed use them on future deals.Then use option B and C together get the 15% down from the 230k you will have available and then use the 500 LOC to cover the rest of the purchase this will maximize your funds.

Is there someone that this community would recommend who could help with establishing a business entity (be it a partnership, LLC or something else I'm not aware of) so that we can buy and sell real estate investments in a smart and careful way?

Establish your end goal and start working towards it.

Were these motivations establish early on or was it a slow realization after a seasoned career?

You'll gain respect and actually get your rent.When you rehab these houses don't spend a lot of money... its not needed an it'll look pretty bad in less than a year.