There are a few places where you can find cheap used CNC vertical machining center machines. Some options include:

1. Online marketplaces: Websites offer a wide variety of used CNC machines at different prices. You can search for machines based on your specific needs and budget.
2. Used machinery dealers: There are many used machinery dealers who specialize in selling CNC machines. They often have a variety of machines in stock, and they may be able to offer a warranty or maintenance services.
3. Manufacturing companies: Some manufacturing companies upgrade their equipment frequently, and they often sell their used machines at a lower price. You can contact companies in your area and ask if they have any used CNC machines for sale.
4. Trade shows and auctions: Trade shows and auctions are a good place to find used CNC machines at a discounted price. You can often find used CNC machines at trade shows for the manufacturing industry, as well as government and industrial auctions.
5. Social Media groups and community groups: There are many groups or communities on social media platforms that are dedicated to discussing and buying/selling CNC machines. These groups are a good place to find used CNC machines at a good price and also to get advice on buying used machines.

It’s important to note that when buying a used machine it’s important to inspect and test the machine before purchasing it, to make sure it meets your requirements and is in good working condition.