I'm open to thoughts on where to invest or other potential methods for a first timer. 

New flooring, kitchen, bathrooms, light fixtures, trim, doors, etc.

I've heard from several people who thought they had an owner finance agreement signed at the kitchen table, assumed they were paying down equity only to have the house sold right out from under them.Ben,  How common is this that a seller is willing to give up their deed upfront in exchange for seller financing.  

Most lenders will likely not lend to a first timer anyways, and if you can find one, they will typically require more down payment, higher fees and higher interest, all of which will make your flip harder to pencil.Second, your flip WILL go over budget, and likely a good amount.  

New kitchen, bathrooms, paint.

We put in around $30,000 to replace the roof, floors, paint and kitchen.

Bathrooms and kitchen upgrades tend to add the most value relative to the money spent on rehabs.

Pretty much all major components were newly installed / fitted and done to a tasteful standard (new metal roof, plumbing, electrical, kitchen, flooring, bathroom, doors, new hvac, decks, vinyl siding etc) and I have visited and walked through 3 times and even been under crawl space to inspect a repair that was previously noted on an inspection to the foundation after termite treatment which looked to be a good job.

I presume they had a kitchen sink, so the sink is not a relevant issue related to habitability.

Complete renovation- flooring, bathroom, kitchen, some windows, trim, paint, etc...