No Support Structure
If there is one thing I've learned in the TV antenna business, it is that buyers are eventually going to need help. They will have questions on a failed setup or positioning or optimizations, and if the antenna manufacturer they purchased from is an unknown with no support, they will be left to figure it out on their own.
How can I tell if support is available?
Do a search for their website on Google. Every company that plans on supporting their customers will have a website with various ways to contact them. Sometimes this will consist of a ticket system, a phone number or more detailed instructions online.
If you cannot find this type of support online, then expect to be on your own if you have trouble. Respectable antenna manufacturers will make sure you've bought one of their products before offering up support. Don't be left out in the cold when you need help.
What type of support will I need?
Being in the antenna business for the last 3 years, I've seen it all. Sometimes customers need help before they've ever purchased an antenna. Some other buy a product and realize they are well over their head once it doesn't work the first time.
Many setup questions are easy to answer, or at least have a very structured way to go about diagnosing them, but without that support structure in place, you aren't going to have any help. Your only options are to hope to return the product for a full refund or to eat the money you've laid out. Unfortunately neither are very good options when you have a $123 Cable TV bill you are trying to replace.