I am interested in building more new rental units with alternative energy features that will produce rental income and residual income from energy systems.

Each time I have made the jump to the newer technology, I have found that very shortly someone will come out with a better product with more features.  

When I look at a property that old I will pull all properties built up to about 1970 and then separate them by style and features.

Of course a lot depends on the location, unit layout and size, features, etc. and having what renters are looking for most.

I haven't been around for 10+ years so maybe they called it something different back in the day but I don't think REST means anything in the context of real estate investing (REI is a common acronym for Real Estate Investing).Aside from that, you should be able to find a ton of information through Bigger Pockets on the topics you're interested in by using the search feature.  

The feature I like the most is the "search" feature.  

They attend seminars featuring a variety of investment options offered by many different lecturers.

Just my opinion but unless it's in an amazing location or has some extra amazing feature, the money, time, and energy it would take to get a construction crew to level the floor is not something I want on my plate especially if the return isn't going to be that significant. 

Intuit just shut down their awesome awesome service of Intuitpaymentnetwork which charges 50cents / payment and had these awesome features like auto request payment.  

There was several podcasts featuring military members and teh challenges of out of state land-lording, and I believe @Brandon Turner did a webinar that featured REI while being Active Duty Military .