It was riskier than a quick cosmetic flip as it had septic issues, was on a busy road, only had 3BR (most in this area have 4) and needed some reconfiguration of space to optimize value.

What are the basic "laws of physics" in rental real estate markets when it comes to optimizing returns?

They should be able to refer you to a few agents who have experience working with investors and can help you understand the market & comps better.While long-term investing may not be optimal for most, a huge positive from it is that it takes away the emotion from investing, so you will rely more heaily on your numbers.

You simply cannot provide the traffic those sites can produce for your rental and in my humble opinion your efforts are probably better spent optimizing and improving within there to maximize your rental numbers.  

It did $82k in gross revenue last year with property management, poor listing optimization, and 30 days of lost revenue.

Seems like you should focusing on optimize this revenue stream. 

A dedicated website will take a little time and some understanding of SEO (Search Engine Optimization), but it's a great low cost way to communicate with current and prospective tenants.

I would say may that post on this site probably know more than an adviser would about placing funds optimally.

But, you need to decide which are most important to you and build your business in such a way as to optimize for what you're not getting.For example, in my business, I demand "better," prefer "cheaper," and am willing to settle for not getting "faster."

I agree taking a prep course is an optimal way to study information in a timely manner.