If you already have a preliminary site layout showing the size and quantity of buildings you can put on the lot, you should be able to take that work on some budget construction costs and from there work your possible rents into the equation to see if what you have drawn makes sense cost wise, or if there is a more efficient way to lay the site out and reduce costs. 

If its zillow or a site like that it may not be accurate.

I have done my reading on Out of State Investing and Section 8 rentals (talked to local HUD sites). 

Go to Etsy and search for "rental property tracker," and you will find hundreds of nice spreadsheets to track 10-20 rentals, usually for under $10.Software has extremely helpful features like online payments, marketing syndication (click a button, and your property is advertised on multiple sites), electronic document review/signing, maintenance tracking, and owner reports.

But as noted, this GC was on site doing work on the house.  

I haven't found very much on this site. 

Welcome to the site!

Long story short, they recommend a process that basically looks like...Soil scientist --> (septic engineer IF needed) --> site plan --> county approval...We've spoken to a few soil scientists and they all quote 2k-5k to analyze the property for an appropriately sized septic system. 

You should join local area Facebook and Meetup sites. 

I'm still new to the site.