I have in the past hooked up cameras and paid for wifi until the house sold or rented, but setting  up and then cancelling the service was very expensive too.

Installing a camera seems like a good idea, but it won't really stop the issue in my opinion. 

Looking for best recommendations when it comes to security cameras, motion sensor lights, key pad locks, ring cameras?

I would set up outside cameras and deadbolts on all doors. 

Fire Dept arrives and garage door is melted, car is melted.Guests call us the next day and tell us the neighbors shot fireworks and hit the house and started the fire and we owe them for damages.We get 3 different camera angles from neighbors clearly showing everything. 

Having MTRs that are equipped with the tech you need (like keyless locks and cameras) helps make management easier.

Do you have a recording camera onsite to help you monitor the work when you're not there?

You might need to get surveillance cameras to help, but I would stay on it aggressively until you get it under control.

Finally, I had to cut ties with the original contractor, get him to leave the house, change locks, put internet, surveillance systems, cameras and blocked him. 

About 6 months into the lease, he thinks he smells smoke and climbs in the attic and searches for 3 hours for "hot spots" using a thermal imaging camera (keep in mind he is the town fire marshall),  finally after not finding any hot spots in the attic he goes to the back yard and discovers the neighbor is BBQing.