What indicators do investors really look for that lets you know whether the market is up, down, or trending in a certain direction?

You can get an idea of what the trends in the neighborhood are. 

@Victoria Coleman population trend is towards moving south.

I'll have to do some research on the trends, but I would hate to get stuck with it if there is a serious market correction and I'm 2K miles away. 

The small single family market in worcester and surrounding towns is seeing a price decline, and due to the typical weather trends in sales, there will be some dips. 

However, the new buyer will also see the positive trend and understand why it was lower when we acquired it.

I have rentometer, I need more than that like rules and regulations, laws, trends, rental comps, etc.

Get to know the market, understand the current cap rates, rent rates, rent trends, affordability rates, population growth, job growth, etc. 

A few things could reveal demand - vacant housing rate in the area, population growth trend, recent and future job growth. 2.

Let's take a look at general trends:1) If you are in the top 20% price range for your area, some of those folks will downsize into median range (40-80%)2) If you are in the middle, many folks will stay put, and you'll get a few down-sizers from above and lose a few to a lower bracket.3) If you're in the bottom (0-39%) these are the folks most at risk of crashing out because they have no plan and no cushion when the bad times hit.