How to get Google Maps API Key for your website
Login & Select Maps
Please go to Google API Console. and login with your google account. Once logged in it will display a popup so pick Maps from it.
Select a New or Existing Project
Create a new project or select an existing project then click on Continue to enable the API and any related services.
Activate Billing for your Account
On the next step you have to create a billing profile. You can consult the Official Guide of Google to learn how you can activate billing for you account.
After creating the billing profile navigate to the Console and click on APIs from the right navigation.
Restrict the API Key to your Domain Only
After activating both APIs in the previous step now click on the Navigation Menu and select APIs & Services and click on Credentials.
In this section, you will see the name of your API Key (so click on it) and restrict it by adding your site URLs (in 3 formats: yourdomain.com, .yourdomain.com and *.yourdomain.com/) as shown in the screencast below.
If you don't restrict the Google Maps API Key then anyone can use it on his website because the API Key is exposed in the code. So, you must restrict the API Key to your domain only.
Copy the API Key and Add it
Copy the generated Google Maps API key from the popup. Click on Close button to proceed after you copied the API Key.
Put this API Key you just copied in Maps Settings (Easy Real Estate → Settings → Maps → Google Maps API Key).
Default Location for Maps on Single Property & Property Listing Pages
In this Maps settings tab, you can also provide the default location for New Property Map and Properties Listing Map (when there is no property to display).
If you are running the RealHomes Theme older than 3.9.0 version then related settings can be found by navigating to Dashboard → Real Homes → Customize Settings → Map
Verify Domain with Google: https://support.google.com/webmasters/answer/35179