This is the example of working plist to run Appium server using launchctl on Mac. See comments for more info and steps how to use this.

com.company.appium.server.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>KeepAlive</key>
	<dict>
		<key>SuccessfulExit</key>
		<false/>
	</dict>
        <key>Label</key>
        <string>com.company.appium.server</string>
        <key>RunAtLoad</key>
        <true/>
	<key>ProgramArguments</key>
	<array>
		<string>/usr/local/bin/node</string>
		<string>/usr/local/lib/node_modules/appium/build/lib/main.js</string>
	</array>
	<key>StandardOutPath</key>
	<string>/Users/path/to/logs/stdout.log</string>
	<key>StandardErrorPath</key>
	<string>/Users/path/to/logs/stderr.log</string>
	<key>EnvironmentVariables</key>
        <dict>
            <key>ANDROID_HOME</key>
            <string>/path/to/android-sdk</string>
            <key>JAVA_HOME</key>
            <string>/path/to/java-home</string>
            <key>PATH</key>
            <string>/content/of/path/env/var</string>
        </dict>
</dict>
</plist>