You can buy some inexpensive security cameras and do your own monitoring. For example, a company such as Wyze Cam can provide a security camera for about $20 that is quite versatile. It can provide you alerts when it senses motion and you can see the video right on your smartphone. It can even provide night vision and other neat features. It stores video for a rolling two week period for free on the cloud for you to access.
Other affordable security systems to consider include Simplisafe, Alfred, and piper. Simplisafe is a well know brand name and offers a reliable product. Piper (about $150 for camera and no monitoring charges) is another reasonable product. Also an app like Alfred allows you to re-purpose any Android or IOS device into a security camera, which makes this the most economical choice for the frugal individual.
I’m not a fan of the expensive systems with expensive monitoring and contracts. I don’t like getting locked in to something that is expensive. I did have a monitoring service with one of the major brand names at one time and it was quite expensive. This premium service might be the right choice for some but I prefer some of the other “no strings attached” products as mentioned above.