These are professionals with additional training and a stricter code of ethics.

@Alex Furini Look at the code under 334-10  Permitted Increases.  

I could change the codes for the locks and shut off the A/C after the guests leave.

I am thinking to install a wifi smart lock on the front door, so guest can come in the front door with a digital code.

When I had my rentals there, the noxious weed board was bothering me at least twice a year, sprinkler back-flow preventers have to be tested every year (after getting a full plumbing permit to install it), code enforcement is insane. 

The landlord-tenant laws in NJ tend to favor tenants.Here are two websites you should look at:https://www.state.nj.us/dca/divisions/codes/office...https://lsnjlaw.org/Publications/Pages/Manuals/Ten...What kind of rental agreement have they signed?

Is there a way to get average home prices, rental prices, and sq ft, etc by zip code/city/county?

@Christian Nachtrieb first find out what the rules are in your local area about inspecting the property – that will be in the property code – you will want to know if they have vacated the premises sooner rather than later that way you can consider it abandoned and if it has, you can move on with your life by taking the appropriate steps to deal with an abandoned property - this should also be spelled out in the property code

The best areas are Germantown and Collierville but very low cap rates. neighborhoods in memphis zip codes change street by street so please do your due dilligence before investing through wholesalers//MLS//Turnkey...

I was surprised to find such a web of laws.Here is the framework: https://law.justia.com/codes/maryland/2017/real-pr...